Apparatus and Method for Determining an Order of Power Devices in Power Generation Systems

ABSTRACT

Various implementations described herein are directed to determining an order of power devices connected in a serial string to a central power device. The physical order may be stored in a non-volatile computer-readable storage medium.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. non-provisional patentapplication Ser. No. 17/979,133, filed Nov. 2, 2022, which is acontinuation of U.S. non-provisional patent application Ser. No.17/355,810, filed Jun. 23, 2021, (now U.S. Pat. No. 11,538,951), whichis a continuation of U.S. non-provisional patent application Ser. No.16/784,980, filed Feb. 7, 2020, (now U.S. Pat. No. 11,081,608), which isa continuation-in-part of U.S. non-provisional patent application Ser.No. 16/217,679, filed Dec. 12, 2018. (now U.S. Pat. No. 10,599,113),which is a continuation-in-part of U.S. non-provisional patentapplication Ser. No. 15/447,981, filed Mar. 2, 2017, (now U.S. Pat. No.10,061,957), which claims the benefit of U.S. provisional application62/381,298, filed Aug. 30, 2016 and U.S. provisional application62/303,017, filed Mar. 3, 2016, which are hereby incorporated byreference in their entireties.

BACKGROUND

Photovoltaic (PV) installations may include a large number of componentsand wide variety of devices. A PV installation may include one or morearrays of PV generators (such as solar modules, solar cells, solarpanels), one or more inverter(s), communication devices, and PV powerdevices such as DC/DC converters. DC-AC microinverters, combiner boxes,and Maximum-Power-Point-Tracking (MPPT) devices. Some installations mayfurther include batteries. Some of the electronic modules may beintegrated with the PV modules and may provide other functions such asmonitoring of performance and/or protection against theft. In case ofthe system experiencing power loss or in case of a potentially unsafecondition, it may be desirable for a system maintenance operator tophysically locate a particular device (such as solar panel, DC-DCconverter or micro-inverter) that may be potentially responsible for thepower loss or potentially unsafe condition.

Operators and monitoring bodies of PV installations might not alwayshave access to a map which indicates the location of each PV module,identified by a serial number. In such cases, troubleshooting problemsmay be time consuming, since locating a specific module, such as amalfunctioning module, may be difficult. In other instances, a map ofthe installation may be obtained by significant manual effort, such as amaintenance worker walking through the installation and copying IDnumbers off modules, denoting their location on a map. When performedmanually, human error may also cause inaccurate information to berecorded in the maps.

There is a need for an automatic or semi-automatic method of generatingphysical maps of PV installations, to save work and reduce errors, whileallowing system monitoring personnel to obtain the benefits of having amap which indicates the locations and ID numbers of PV modules.

SUMMARY

The following summary is a short summary of some of the inventiveconcepts for illustrative purposes only, and is not intended to limit orconstrain the examples in the detailed description. One skilled in theart will recognize other novel combinations and features from thedetailed description.

Embodiments herein may employ methods for generating maps of PVinstallations. Some illustrative embodiments may be fully automatic, andsome may require manual steps.

In illustrative methods, a suitable localization algorithm may beutilized to measure or estimate the global coordinates of photovoltaic(PV) devices, and/or the distance and/or angle between differentdevices, and/or the distance and/or angle between devices and knownlocations. Some embodiments may include obtaining the global coordinatesof devices. Some embodiments may produce a map displaying the physicalplacement and location of devices along with identifying information(such as ID or serial numbers). Some embodiments may utilizehigh-accuracy Global Positioning System (GPS) technology to map theinstallation. For example, some illustrative methods may includescanning an identifying barcode on PV devices while using GPS to obtainthe global coordinates at each scanned location. In some embodiments, amap not including identifying module information may be further utilizedto match specific modules to the measured GPS coordinates. Someembodiments may include PV devices transmitting and receiving wirelesssignals from one another, and using measured or estimated quantitiessuch as Received Signal Strength Indication (RSSI). Angle of Arrival(AOA, also known as Direction of Arrival, or DOA) and/or Time Differenceof Arrival (TDOA) to estimate relative distances and/or angles betweenmodules. In some embodiments, Power Line Communication (PLC) methods maybe used along with Time Domain Reflection (TDR) techniques to estimatethe location of a set of PV devices within a PV installation. The set ofestimates may be processed to obtain an accurate physical map of theinstallation, including identifying where each PV module and/or PVdevice is physically located.

In other illustrative methods, photovoltaic modules may be operated toincrease and decrease the electrical power produced by the photovoltaicmodules, which may result in a change of temperature at the photovoltaicmodules. A thermal imaging device may be used to capture thermal imagesof a group of photovoltaic modules under different power production andtemperature conditions, and suitable methods may analyze and aggregatethe thermal images to obtain an accurate physical map of theinstallation.

In other illustrative methods, aspects of electronic systems may be usedto determine the order of photovoltaics (PV) panels connected in aserial string. Each PV panel may be connected to an electronic device(such as a power converter) as an intermediate device between the PVpanel and the serial string. The device may set or change an electricalparameter, such as an impedance, a voltage, and/or the like, measured orreflected at the electrical conductor that serially connects PV panels.When a device connected as part of the string, such as a deviceconnected at the end of the string, the middle of the string, thebeginning of the string, and/or the like, transmits a signal along theconductor, the power devices (such as devices including converters) mayeach measure the received signal at each power converter and transmitthe recorded signal to the same or a different device to analyze theorder of the devices of the string.

In other illustrative methods, an order of power devices connected in aserial string may be determined. A command is transmitted, to at leastone first power device of a plurality of power devices, to change anoutput electrical parameter. At least one electrical signal is caused tobe transmitted from at least one second power device of the plurality ofpower devices. At least one measured value responsive to the electricalsignal is received from at least one of the plurality of power devices.A determination is made, by analyzing the at least one measured value,which ones of the plurality of power devices are ordered in the serialstring between the at least one first power device and the at least onesecond power device.

In other illustrative embodiments, a power device includes acommunication interface configured to receive commands; at least onehardware controller, at least two output conductors; and an adjustmentcircuit configured to adjust an output electrical parameter of at leastone of the at least two output conductors. The adjustment is responsiveto the received command, and wherein the at least one hardwarecontroller is configured to (i) perform the adjustment based on thereceived command, and (ii) measure an electrical signal transmitted onat least one of the at least two output conductors.

In other illustrative embodiments, an ordering of power devices of apower generation system is provided, wherein the power devices areconnected in a serial string. The power generation system includes aplurality of power devices each comprising a plurality of electricaloutput conductors, wherein each of the plurality of power devices isconfigured to adjust an electrical output parameter of the plurality ofelectrical output conductors. The power generation system also includesat least one transmitting power device of the plurality of power devicesconfigured to transmit an electrical signal. The power generation systemfurther includes at least one receiving power device of the plurality ofpower devices configured to receive and record the electrical signal,wherein the at least one receiving power device comprises acommunication interface for sending a recorded electrical signal. Thepower generation also includes at least one hardware processor. Thehardware processor is configured to command at least one of theplurality of power devices to adjust an electrical output parameter. Thehardware processor is also configured to command the at least onetransmitting power device to transmit the electrical signal. Thehardware processor is further configured to command the at least onereceiving power device configured to receive the electrical signal,record at least one value of the electrical signal, and send therecorded electrical signal value. The hardware processor is alsoconfigured to receive the recorded electrical signal values. Thehardware processor is still further configured to analyze the recordedelectrical signal values to determine an ordering at least in part ofthe plurality of power devices.

As noted above, this summary is merely a summary of some of the featuresdescribed herein. It is not exhaustive, and it is not to be a limitationon the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentdisclosure will become better understood with regard to the followingdescription, claims, and drawings. The present disclosure is illustratedby way of example, and not limited by, the accompanying figures. A morecomplete understanding of the present disclosure and the advantagesthereof may be acquired by referring to the following description inconsideration of the accompanying drawings, in which like referencenumbers indicate like features, and wherein:

FIG. 1 is a flow diagram of a method for generating a photovoltaic (PV)installation map, according to one or more illustrative aspects of thedisclosure.

FIG. 2A is a flow diagram of a method for fitting measured locations toa map, according to one or more illustrative aspects of the disclosure.

FIG. 2B illustrates a non-identifying map (NIM), according to one ormore illustrative aspects of the disclosure.

FIG. 2C illustrates an estimated layout map (ELM), according to one ormore illustrative aspects of the disclosure.

FIG. 2D illustrates how illustrative methods may be applied toillustrative PV systems, according to one or more illustrative aspectsof the disclosure.

FIG. 3A is a flow diagram of a method for generating an installation mapbased on time and location, according to one or more illustrativeaspects of the disclosure.

FIG. 3B is a flow diagram of a method for mapping samples to strings,according to one or more illustrative aspects of the disclosure.

FIG. 4 illustrates an illustrative of representing and storing aNon-Identifying Map, according to one or more illustrative aspects ofthe disclosure.

FIG. 5A is a flow diagram of a method for generating a Non-IdentifyingMap, according to one or more illustrative aspects of the disclosure.

FIG. 5B illustrates a user interface for PV installation mapping,according to one or more illustrative aspects of the disclosure.

FIG. 6 illustrates an illustrative embodiment of reading identifyinginformation from a PV device and estimating the device location,according to one or more illustrative aspects of the disclosure.

FIG. 7 illustrates illustrative devices which may be used for readingidentifying information and/or estimating device location, according toone or more illustrative aspects of the disclosure.

FIG. 8A is a flow diagram of a method for installation mapping,according to one or more illustrative aspects of the disclosure.

FIG. 8B illustrates results of various stages of installation mapping,according to one or more illustrative aspects of the disclosure.

FIG. 9 is part-block diagram, part schematic of an illustrative PVinstallation that may be mapped, according to one or more illustrativeaspects of the disclosure.

FIG. 10 is a flow diagram of a method for grouping power devices intogroups, according to one or more illustrative aspects of the disclosure.

FIG. 11A is a part-block diagram, part-schematic of PV system componentswhich may be used in conjunction with methods described herein.

FIG. 11B is a schematic of illustrative variable impedance circuits,according to one or more illustrative aspects of the disclosure.

FIG. 11C is a schematic of illustrative conductor networks, according toone or more illustrative aspects of the disclosure.

FIG. 11D is a schematic of illustrative conductor networks, according toone or more illustrative aspects of the disclosure.

FIG. 12A illustrates an illustrative form of a wave reflected off atransmission line, according to one or more illustrative aspects of thedisclosure.

FIG. 12B illustrates an illustrative form of a first wave received atdevices along a transmission line, according to one or more illustrativeaspects of the disclosure.

FIG. 12C illustrates an illustrative form of a second wave received atdevices along a transmission line, according to one or more illustrativeaspects of the disclosure.

FIG. 12D illustrates an illustrative form of a third wave received atdevices along a transmission line, according to one or more illustrativeaspects of the disclosure.

FIG. 12E illustrates an illustrative form of a signals received atdevices along a transmission line, according to one or more illustrativeaspects of the disclosure.

FIG. 13 is a flow diagram of a method for testing power devices,according to one or more illustrative aspects of the disclosure.

FIG. 14 is a part-block diagram, part-schematic of a PV arrangement,comprising PV system components, which may be used in conjunction withmethods described herein.

FIG. 15A is a part-block diagram, part-schematic of a PV panel and PVsystem components which may be used in conjunction with methodsdescribed herein.

FIG. 15B is a part-block diagram, part-schematic of PV system componentswhich may be used in conjunction with methods described herein.

FIG. 16 is a flow diagram of a method for grouping power devices intostrings, according to one or more illustrative aspects of thedisclosure.

FIG. 17A illustrates an illustrative PV string of PV devices, accordingto one or more illustrative aspects of the disclosure.

FIG. 17B illustrates an illustrative current leakage circuit, accordingto one or more illustrative aspects of the disclosure.

FIG. 18 is a flow diagram of a method for determining the order of powerdevices within a PV string, according to one or more illustrativeaspects of the disclosure.

FIG. 19 illustrates illustrative devices which may be used for readingidentifying information and/or estimating device location, according toone or more illustrative aspects of the disclosure.

FIG. 20 illustrates a thermal image of a group of photovoltaic modules,according to one or more illustrative aspects of the disclosure.

FIG. 21 is a flow diagram of a method for determining relative locationsof one or more PV modules within a group of PV modules, according to oneor more illustrative aspects of the disclosure.

FIG. 22 shows an example circuit diagram of a PV string with PV orderdetection components.

FIG. 23 shows example graphs of signal attenuations from signalinjection on DC+ and DC−.

DETAILED DESCRIPTION

In the following description of various illustrative embodiments,reference is made to the accompanying drawings, which form a parthereof, and in which is shown, by way of illustration, variousembodiments in which aspects of the disclosure may be practiced. It isto be understood that other embodiments may be utilized and structuraland functional modifications may be made, without departing from thescope of the present disclosure.

Monitoring of PV installations may include data collected by a centralcontrol system which monitors the power output by the PV installationand identifies potentially problematic operating conditions or safetyhazards. When the installation experiences power loss, it may bedesirable to ascertain whether it is due to environmental conditions orfrom malfunctions and/or poor maintenance of the components of the PVinstallation. Furthermore, it may be desirable to easily physicallylocate the particular module (such as solar panel. DC-DC converter ormicro-inverter, combiner box) that may be responsible for the powerloss. A map of the PV installation which displays the physical locationof the various PV modules or devices (identified by ID numbers, forexample) comprising the installation may assist in rapid location of thedesired module and fast resolution of the problem. For example, in caseof a decrease in the power output by a PV panel, a power device coupledto the panel may send information to a centralized control unitreporting the loss of power. The information may be transmitted usingpower line communications, wireless communication, acousticcommunication or other protocols, and may include the ID number of thePV device. When the low power output persists, a maintenance worker mayneed to physically go to the underperforming panel and investigate thereason behind the low power.

A Physical Identification Map (PIM) may refer to a physical mapindicating the location of modules within a photovoltaic (PV)installation, including attaching identifying information such as serialor ID numbers to some or all of the modules displayed in the map. ANon-Identifying Map (NIM) may refer to a map that describes the locationof modules but does not identify a specific module at each location.

FIG. 1 is a flow diagram of a method for generating a PV installationmap according to one or more illustrative aspects of the disclosure. Inone or more embodiments, the method of FIG. 1 , or one or more stepsthereof, may be performed by one or more computing devices or entities.For example, portions of the method of FIG. 1 may be performed bycomponents of a computer system. The method of FIG. 1 , or one or moresteps thereof, may be embodied in computer-executable instructions thatare stored in a computer-readable medium, such as a non-transitorycomputer-readable medium. The steps in the method of FIG. 1 might notall be performed in the order specified and some steps may be omitted orchanged in order.

At step 100, an initial map of a PV installation layout may be created.The initial map may be a physical map. For example, at step 100,measured Global Positioning System (GPS) coordinates may be used tomatch modules to physical locations on a PIM. The initial map may becreated and represented in various ways. In one implementation, theinitial map may be represented as a text file which includes informationregarding the number of devices, the number of rows, the distancesbetween devices, the distances between rows, or any other informationrelevant to the physical layout of the installation. In anotherimplementation, the basic map may be automatically generated byinstallation-design software, and the layout information may be encodedin a digital file generated by the installation-design software.

In some embodiments, step 100 might not be performed. For example, step100 might not be performed when there is high enough accuracy in othersteps of the method to compensate for the lack of an initial map.

In steps 110-13, power modules in the PV installation may be scanned.For example, the power modules may be scanned by rows. At step 110 eachdevice in a row of the PV installation may be scanned. The scanning maybe carried out using a locating device that combines scanningcapabilities with a GPS receiver. The locating device may furtherinclude one or more of a clock, memory, communication means and aprocessing unit. Scanning may comprise utilizing a barcode reader toread a barcode which is attached to the module being scanned (such as abarcode on a sticker which is stuck to the module), utilizing a camerato identify serial numbers, obtaining identifying information from anRFID tag, or any combinations thereof. The locating device may be asmartphone running an application which combines barcode reading orserial number identifying with GPS localization. The scanning maycomprise taking a picture of an identifying element of the module (suchas an identification sticker) which may later be processed to identifythe module based on the picture. In some embodiments, in step 111 theuser may configure the device (such as by press of a button) at thestart of each row to begin logging a row of the installation. In someembodiments, the locating device may use time or spatial differencesbetween scans to determine when a new row is being scanned. For example,when a time between scans is above a certain threshold, the locatingdevice may determine that a new row is being scanned.

At step 112 each PV device in the current row may be scanned. Each timea device is scanned, the module's identifying information (such asbarcode, ID number, picture, RFID tag) as well as the GPS coordinates ofthe locating device at the time of scanning may be logged and storedinto memory. The identifying information corresponding to a device maybe unique. A timestamp of the time of scanning may also be logged orstored.

At step 113 it may be determined when all rows of the installation havebeen scanned. For example, it may be determined when all rows within aspecified area have been scanned. When all rows have been scanned, themethod may proceed to step 120. Otherwise, steps 110-13 may be repeated.Steps 110-13 may be repeated until all rows of the installation, or alldevices within the installation, have been scanned.

At step 120, the data (such as coordinates, timestamps) collected duringsteps 110-13 may be collected and input to a matching algorithm. The mapcreated in step 100 may also be input to the matching algorithm.

At step 130, the matching algorithm may be run by an appropriatecomputing device, such as a computer, server. DSP, microcontroller, ASICor FPGA. The algorithm may use the inputted data and/or the map todetermine which PV module is located at each of the locations indicatedon the map. FIG. 2A, further described below, is an example of a methodthat may be used by a matching algorithm at step 130.

At step 140, the matching algorithm may generate, based on the inputreceived at step 120, a map of the PV installation. The map may compriseone or more module identifiers. The module identifiers may be associatedwith a location in the map. For example, the algorithm may output a mapwith module identification information being displayed at each module'slocation. The map may be physically printed onto a sheet of paper, orviewed on an appropriate electronic device such as a computer monitor,tablet or smartphone.

FIG. 2A is a flow diagram of a method for fitting measured locations toa map according to one or more illustrative aspects of the disclosure.In one or more embodiments, the method of FIG. 2A, or one or more stepsthereof, may be performed by one or more computing devices or entities.For example, portions of the method of FIG. 2A may be performed bycomponents of a computer system. The method of FIG. 2A, or one or moresteps thereof, may be embodied in computer-executable instructions thatare stored in a computer-readable medium, such as a non-transitorycomputer-readable medium. The steps in the method of FIG. 2A might notall be performed in the order specified and some steps may be omitted orchanged in order.

At step 131, a map and/or GPS coordinates may be received. For example,the map and/or GPS coordinates may be loaded from memory. The map and/orGPS coordinates may have been measured when scanning PV modules. Thereceived map may comprise a non-identifying map (NIM), which might notinclude identifying module information.

At step 132, the GPS measurements may be grouped into rows. In someembodiments, the grouping into rows may be done while scanning one ormore modules. For example, a scanning operator may press a reset buttonwhen beginning to scan, or prior to scanning, each row. In someembodiments, the grouping of measurements into rows may be carried outby a computer algorithm, using methods further described herein. Thegrouping of measurements into rows may be helpful, for example, when thePIM is generated using an NIM, which already indicates the number ofrows and the length of each row. In embodiments in which the PIM isgenerated without benefit of a pre-existing NIM, the grouping into rowsmay allow for filtering of measurement noise. For example, filtering, orreduction, of measurement noise may be performed by determining thestandard distance and angle between adjacent panels in a same row. Steps133-37 may be performed iteratively, until the first row of scannedsamples has been considered as a candidate to represent each row of theinstallation. At step 133, a row is selected from the NIM. At step 134,the first row of location measurements may be fit to the selected row.At step 135, having fit the first row of location measurements to theselected row, the other rows of measured samples may be fit to the otherrows of the NIM, using “snap to grid” or similar methods. In someembodiments, attempted fitting of the other rows of measured samples tothe other NIM rows may be carried out multiple times, using multiple roworientations, before an optimal fitting (by an appropriate criterionsuch as Least Squares) is selected.

At step 136, a total fitting error may be calculated. The total fittingerror may be based on the estimated locations of each device and/or thelocations indicated by the NIM. Estimated individual errors of eachdevice may be aggregated by an appropriate criterion, such as Sum ofSquares. The selected fitting and resultant aggregated error may bestored. For example, the selected fitting and resultant aggregated errormay be stored in an appropriate memory device.

At step 137, the method may determine when all NIM rows have beenconsidered as the row represented by the first row of measurements. Whensome NIM rows have not been considered the method may loop back to step134. For example, the NIM rows that have not been considered may becandidates for consideration in later iterations. When it is determined,at step 137, that all NIM rows have been considered, the method mayproceed to step 138.

At step 138, one or more aggregated errors calculated and stored at step136 may be compared to one another to select a fitting. In oneimplementation, a fitting corresponding to the minimum aggregated errormay be selected. Other factors may be considered at step 138.

At step 139, the fitting selected at step 138 may be output,transforming the NIM to a PIM that includes the fitting selected at step138. In some embodiments, steps 134-37 may be modified such that insteadof fitting the first row of measurements to each row in the NIM, eachrow of measurements is fitted to a certain row of the NIM (for example,the first row of the NIM).

Reference is now made to FIGS. 2B and 2C, which depict illustrativeexamples of a PV installation which may be mapped according toillustrative embodiments. FIG. 2B illustrates a Non-Identifying Map(NIM) 215 that may be generated, using methods described herein, toreflect a layout of the PV installation. FIG. 2C illustrates anEstimated Layout Map (ELM) 217 of the installation, which may beobtained using methods described herein to estimate the absolutelocations of PV devices or the locations with regard to one another.FIGS. 2B and 2C may correspond to a same PV installation.

In FIGS. 2B-D, the illustrated squares may correspond to devicelocations according to the NIM, and the circles may correspond to devicelocations according to measured data corresponding to the devices. Incertain instances, the PV system may be of a non-symmetric layout. Forexample, in the NIM 215, one row has two fewer devices than the othertwo rows. In certain instances, because of measurement inaccuraciesand/or noise, an ELM, such as the ELM 217, may contain inaccuracies.

Reference is now made to FIG. 2D, which illustrates aspects of steps134-36, described above in FIG. 2A, as applied to the PV systemillustrated in FIGS. 2B-C. In Fitting A, at step 133, the first row ofthe NIM is selected. At step 134, the first row of location measurementsis fit to the selected first row of the NIM, and at step 135 theremaining two rows are fit to the NIM in a way that minimizes the totalmismatch between the NIM-devices (depicted as squares) and the ELMdevices (depicted as circles). At step 136, the total fitting error iscalculated. Different error measures may be considered. For example, asum-of-squares error measure may be considered. If, for example, threedevices are estimated to be at the following locations along theXY-plane: (0,0). (1,0) and (2,0), while according to the NIM the threedevices are actually located at (0,0.5), (1, 1.5) and (2,0), the squareof the estimation error for the first device may be(0-0)²+(0-0.5)²=0.25. Similarly, the squared estimation error for thesecond device may be (1-1)²+(0-1.5)²=2.25. The third device location isperfectly estimated, with zero error, leading to a total error of 2.5.Other error measures may be considered as well, such as Sum of AbsoluteErrors, or weighted variations which may take other considerations intoaccount and/or add penalty factors to certain types of errors.

At step 137, the method may loop back to step 133, as the first row ofmeasurements has been fit to the first NIM, and other map rows have notbeen fit. At step 134, the first row of measurements is fit to thesecond NIM row, and at step 135, the other EL rows are “snapped” to theNIM and fitted to the other NIM rows, as shown in Fitting B. Thematching illustrated in Fitting B is less successful than the one shownin Fitting A. and the fitting error calculated in step 136 may behigher. At step 137, the method may determine that the first row ofmeasurements has not yet been fit to one of the NIM rows (the third),and it may loop back to step 133 and select the third NIM row. At step134, the first row of measurements may be fit to the third NIM row, andat step 135, the other EL rows may be “snapped” to the NIM and fitted tothe other NIM rows. Several fittings are possible, as illustrated byFitting C and Fitting D. and by various methods the algorithm may beconfigured to consider multiple fittings and select one of the fittings,for example, a fitting with minimal estimation error or a leastestimation error. At step 136 the fitting error may be calculated, andat step 137 the algorithm may determine that the first row ofmeasurements has now been fit to all of the NIM rows, and may proceed tostep 138. At step 138, the algorithm may determine that Fitting A hasthe lowest estimation error of all the fittings considered, and mayoutput Fitting A at step 139.

FIG. 3A is a flow diagram of a method for generating an installation mapbased on time and location according to one or more illustrative aspectsof the disclosure. In one or more embodiments, the method of FIG. 3A, orone or more steps thereof, may be performed by one or more computingdevices or entities. For example, portions of the method of FIG. 3A maybe performed by components of a computer system. The method of FIG. 3A,or one or more steps thereof, may be embodied in computer-executableinstructions that are stored in a computer-readable medium, such as anon-transitory computer-readable medium. The steps in the method of FIG.3A might not all be performed in the order specified and some steps maybe omitted or changed in order.

The method of FIG. 3A may be used for grouping device measurements intorows. For example, the method of FIG. 3A may be performed at step 132 ofFIG. 2A. According to this illustrative embodiment, each row of aninstallation may be processed such that the time that elapses betweenscanning a device in the row and the adjacent device in the row is lessthan a certain threshold, such as, for example, 10 seconds. Theinstaller may be instructed to scan each device in the row rapidly, andtake a short break between rows. The scanning device may be configuredto record the time each device was scanned.

At step 310, a time difference between each pair of consecutive scansmay be calculated. At step 320 the calculated time differences may becompared to a threshold amount of time. In some embodiments thethreshold may be preset or predefined, and in some embodiments thethreshold may be derived from calculated time differences (such as thethreshold may be twenty percent longer than an average time differencebetween consecutive scans). At step 330, when the time differencebetween the timestamps of scanning two consecutive devices is above thethreshold, the two devices may be determined to be in different rows,and may be mapped to different rows at step 340. When the timedifference is below the threshold, the two devices may be determined tobe in a same row, and mapped to the same row at step 350. Alternatively,or in addition to the method described above, the installer may beinstructed to press a “New Row” button on his or her device betweenrows, which may indicate completing the scanning of one row andbeginning another. The “New Row” button may be used to override timingconsiderations, and/or to compensate for inconsistent scanning speed.

FIG. 3B is a flow diagram of a method for mapping samples to stringsaccording to one or more illustrative aspects of the disclosure. In oneor more embodiments, the method of FIG. 3B, or one or more stepsthereof, may be performed by one or more computing devices or entities.For example, portions of the method of FIG. 3B may be performed bycomponents of a computer system. The method of FIG. 3B, or one or moresteps thereof, may be embodied in computer-executable instructions thatare stored in a computer-readable medium, such as a non-transitorycomputer-readable medium. The steps in the method of FIG. 3B might notall be performed in the order specified and some steps may be omitted orchanged in order.

Reference is now made to FIG. 3B, which shows an illustrativeimplementation for grouping device measurements into rows. For example,the steps described in FIG. 3B may be performed at step 132, describedabove in FIG. 2A. According to this illustrative embodiment, each row ofthe installation may be processed such that the distance and/or anglebetween scanned devices may be compared to a reference distance and/orangle. The scanning device may be configured to determine and/orestimate a global position at the time of each scan, by utilizinglocalization systems such as Global Positioning System (GPS). At step315, the estimated distance and/or angle between each pair of scanneddevices may be calculated. At step 325, the estimated distance and/orangle between scanned devices may be compared to a reference and/or athreshold. In some embodiments the reference may be predefined, while inother embodiments the reference may be derived from calculated distances(such as the reference may be the average distance between consecutivescans, with a threshold twenty percent longer than the reference, or thereference may be derived from the angles between consecutive scans, withan appropriate threshold).

At step 335, the distance and/or angle between two devices, which mayhave been scanned consecutively, are compared to the reference distanceand/or angle. If, at step 335, it is determined that the distance and/orangle are above the threshold, the two devices may be mapped todifferent rows, or strings, at step 345. If, at step 335, it isdetermined that the distance and/or angle are below the threshold, thetwo devices may be mapped to a same row, or string, at step 355.Alternatively, or in addition to the method described above, theinstaller may be instructed to press a “New Row” button on his or herdevice between rows, which may indicate him or her completing thescanning of one row and beginning another. The “New Row” button may beused to override distance and/or angle considerations, and/or tocompensate for inconsistent distances and/or angles between devices inthe same row.

Reference is now made to FIG. 4 , which depicts one illustrativeembodiment of representing a Non-Identifying Map (NIM). Generation of arepresentation of an NIM may be included in installation mapping methodsincluding steps such as step 100 from FIG. 1 , which is described above.A PV installation may be represented as a text file which containsinformation regarding the installation. For example, an NIM may berepresented by a text file which lists the rows in the installation, thenumber of devices in each row, and/or the distance between each pair ofdevices. Additional information such as absolute locations of somedevices, row orientation, angles and distances between rows, or otherinformation may be included in the NIM. The mapping method may includean appropriate parser to parse the text file and extract informationfrom the NIM to compare the scanned information to the NIM layout.

FIG. 5A is a flow-chart of generating a Non-Identifying Map. In one ormore embodiments, the method of FIG. 5A, or one or more steps thereof,may be performed by one or more computing devices or entities. Forexample, portions of the method of FIG. 5A may be performed bycomponents of a computer system. The method of FIG. 5A, or one or moresteps thereof, may be embodied in computer-executable instructions thatare stored in a computer-readable medium, such as a non-transitorycomputer-readable medium. The steps in the method of FIG. 5 might notall be performed in the order specified and some steps may be omitted orchanged in order.

FIG. 5A, depicts an illustrative embodiment of generation andrepresentation of a Non-Identifying Map (NIM). For example, the stepsdescribed in FIG. 5A may be performed during the method described inFIG. 1 . A program or application may be used to design and plan a PVinstallation. The program may run on appropriate platforms (PCs,tablets, smartphones, servers, and/or the like), and may be madeavailable to installers and/or system designers. The program may includea Graphic User Interface (GUI) to facilitate in site planning. At step101, the site planner or designer may use the program or application todesign a PV installation using the tools made available by theapplication. For example. FIG. 5B illustrates an example of a userinterface for PV installation mapping that may be used at step 101 ofFIG. 5A to design the PV installation. A user may design a PVinstallation featuring a plurality of photovoltaic generators 501 (suchas PV panels, PV modules. PV cells, strings or substrings of PV panels)and featuring one or more power converters (such as PV inverter 502).

At step 102, of FIG. 5A, a binary file may be generated comprisinginformation describing a portion of or the full layout of the system.The binary file may be generated at step 102 after a layout of the PVinstallation has been designed using the program GUI. Embodiments of thePV installation mapping methods described herein may include reading thebinary file generated at step 102 and extracting site layout informationfrom the binary file.

Reference is now made to FIG. 6 , which shows components for scanning aPV device and logging the time and/or location of the scanner at thetime of scanning. PV device 602 (such as PV panel, optimization device.DC/DC converter, inverter, monitoring device, communication device,and/or the like) may be marked with an ID marker 600 that may be scannedor processed. ID marker 600 may be a barcode that may be scanned by ascanning device. ID marker 600 may be a serial number identifiable by acamera, such as a camera with digit-identification capabilities. IDmarker 600 may be an RFID tag, or a memory device readable by anelectronic circuit. It should be understood that any other type ofmarker may be used in addition to or instead of the listed examples.

Scanning and localization device 601 may capture or record data providedby the ID marker 600. For example, the device 601 may be configured toobtain the identifying information from PV device 602, by scanning,taking a picture of, or retrieving data stored by the ID marker 600.Device 601 may include a clock and memory device, and be configured tostore the timestamp of each scan along with the identifying informationof the device scanned at that time. Device 601 may include alocalization device such as a GPS device, configured to communicate withsatellites 603 and estimate the location of the device at the time ofscanning. In one implementation, the GPS methods employed may allow forestimates with sufficient accuracy to provide differentiation betweenadjacent PV devices deployed in the same installation.

Reference is now made to FIG. 7 , which shows examples of scanning andlocating devices that may be used in conjunction with illustrativeembodiments described herein. Combined device 700 may include one ormore of the illustrated components. ID reader 203 may be configured toretrieve identifying information from a PV device. In some embodiments,ID reader 203 may comprise a camera, and may be configured to take aphotograph of a serial number or other identifying information on the PVdevice. In some embodiments. ID reader 203 may comprise a barcodescanner and be configured to scan a barcode on the PV device. In someembodiments, ID reader 203 may comprise an electronic circuit configuredto read an RFID tag or a memory device storing identifying information.

In some embodiments, the device 700 may include GPS device 201,configured to receive or determine a GPS location, for example, whenscanning a PV device. The device 700 may write (such as record, store,transmit, and/or the like) the ID information and GPS coordinates todata logging device 202. The data logging device 202 may comprise flashmemory, EEPROM, or other memory devices.

Controller 205 may synchronize the various components comprising device700. The controller 205 may comprise a DSP, MCU, ASIC, FPGA, and/or adifferent control unit. The controller may be split into several controlunits, each responsible for different components. Device 700 may includecommunication device 206. The communication device 206 may be configuredto communicate using a wireless technology such as ZigBee, Bluetooth,cellular protocols, and/or other communication protocols. In someembodiments, measurements, timestamps and/or ID information may betransmitted, for example, by the communication device 206, to a remoteserver and/or stored to memory at a remote location. Device 700 mayinclude clock 204, configured to sample, store, and/or communicate thetime (in conjunction with the memory device and/or communicationdevices). For example, the clock 204 may be used to record a timestampeach time the ID reader 203 determines (such as obtains, measures,and/or the like) a device ID.

Device 700 may further include tilt sensor 207, configured to measurethe tilt of the device 700 and store the measurement to memory and/orcommunicate the measurement. The tilt sensor may be used to measure thetilt of PV devices such as PV panel. Scanning device 700 may alsoinclude a compass 208. The compass 208 may be configured to measure ordetermine the direction a PV module is facing. For example, the compass208 may be used to measure a direction of a PV module when a tiltmeasurement is carried out. Determining the tilt of one or more PVpanels and/or the direction that the one or more PV panels face may beuseful for various applications, such as monitoring applications ormapping applications. When the tilt of the PV panels is fixed duringdeployment, the installer may want to measure tilt and angle whilescanning the PV devices for mapping purposes. The scanned data may beuploaded to a remote monitoring device.

In some embodiments, a device such as mobile phone/tablet 710 mayinclude some or all of the functionality described with regard tocombined device 700. Combined device 700 may also include a screen,configured to display the information generated by the device. In oneimplementation, the screen may display information in real-time, whichmay allow the installer to monitor progress, and may improve scanningaccuracy. Many mobile devices include ID readers such as barcodescanners or a camera, a GPS device, controller, communication methods, aclock, compass and tilt sensor. Application software may be downloadedto the mobile device to allow the different components to interact in away that achieves the desired functions described herein with regard tomapping PV installations. The mobile device may allow the installationmap to be displayed on the device's screen while scanning, and showreal-time updating of the information attached to each PV device in thefield, to aid the installer in determining that the information is beingprocessed accurately and clearly.

FIG. 8A is a flow diagram of a method for installation mapping accordingto one or more illustrative aspects of the disclosure. In one or moreembodiments, the method of FIG. 8A, or one or more steps thereof, may beperformed by one or more computing devices or entities. For example,portions of the method of FIG. 8A may be performed by components of acomputer system. The method of FIG. 8A, or one or more steps thereof,may be embodied in computer-executable instructions that are stored in acomputer-readable medium, such as a non-transitory computer-readablemedium. The steps in the method of FIG. 8A might not all be performed inthe order specified and some steps may be omitted or changed in order.

Reference is now made to FIG. 8A, which shows an illustrative method forestimating relative positions of a plurality of PV devices with regardto one another. In one implementation, the position may be estimated, ordetermined, without the use of localization devices, such as satellites.All or a portion of the PV devices in a PV installation may be equippedwith a communication device, such as a wireless transceiver running anappropriate wireless protocol (such as Bluetooth, ZigBee, Wi-Fi, LTE,GSM, UMTS, CDMA and/or the like) or a Power-Line Communication (PLC)transceiver, which may be coupled to the PV installation's cables andconfigured to communicate by sending messages to each other over thecables.

At step 800, a mapping algorithm may be initialized by assigning randomlocations to each of the PV devices that are to be mapped. In oneimplementation, one or more of the devices may begin communicating bybroadcasting an ID number, the current timestamp, and/or otherinformation over the communication medium (such as power cables,wireless channels). For example, the ID number, timestamp, or otherinformation may be transmitted at a predetermined amplitude. All or aportion of the devices may be able to detect the ID signals that arebroadcast by the other devices. The received signal strength and/or thetime it takes for the signal to propagate from one device to the nextmay depend on the distance and signal attenuation between the devices.In some embodiments, the devices may engage in one-way communicationonly, such as each device might only send messages to some or all of theother devices without being configured to receive a response from anyparticular device(s). In some embodiments, two or more devices mayengage in two-way communication (such as Device A sends a message toDevice B requesting a response, and measures the elapsed time betweensending the message and receiving the response).

At step 805, the signal strength of each signal received by each deviceand/or the time delay between sending and receiving messages may bemeasured. At step 810 the signal strength and/or time delay measured atstep 805 may be used to generate one or more initial estimates ofpairwise distances between devices. The initial estimates may compriseerror, such as error due to stochastic attenuation factors, noisychannels, and/or unexpected delays in signal propagation. In oneimplementation, multiple measurements may be taken and then averaged, orsome other function may be applied to the measurements. In thisimplementation, an initial accuracy of the measurements may be improvedby taking multiple measurements.

At step 815, the initial distance estimates generated at step 810 may beinput to an algorithm, which may analyze the initial pairwise distanceestimates and use them to generate an Estimated Layout Map (ELM). Manyalgorithms for this step may be considered, and in some embodiments,combinations of algorithms may offer accurate results. For example, aLeast Squares (LS) problem may be formulated to create an ELM whichminimizes the disparity between the pairwise estimated distances betweenvarious devices. A myriad of other methods, such as simulated annealing,Convex Optimization, Semidefinite Programming, or MultidimensionalScaling may be combined with transliteration and/or triangulationtechniques to obtain an estimated layout based on the measurements.

At step 820, it may be determined whether a non-identifying map (NIM) isavailable. When a NIM is available, the method may proceed to step 840.At step 840, the NIM and ELM may be input to a matching algorithm whichmay incorporate elements of the method illustrated in FIG. 2A, andfurther discussed in FIGS. 2B-D, to match the identifying informationincorporated in the ELM to the device locations described by the NIM. Atstep 845 the matching algorithm may run, such as, execute, and at step850 a map of the installation may be output which outlines the devicelocations along with ID information for each device. The map may be in aformat viewable on an appropriate device, such as a computer monitor,mobile phone, tablet, and/or the like. The map may be representeddigitally or in a textual format.

Alternatively, when no NIM is available at step 820, the algorithm mayproceed to step 825. At step 825 the method may seek “anchor devices”,such as, a set of one or more specific devices which have knownlocations. When such anchors exist (or may be easily obtained by theinstaller), certain device IDs from the ELM may be matched to the knownlocations at step 835, and the rest of the devices may be arrangedaround them, with the final arrangement then output at step 850. When noanchor devices exist or may be obtained, the algorithm may use thecurrent solution without further modification at step 830, proceed fromstep to step 850, and output the ELM “as is”, as a final map of theinstallation with ID information for each device. The method of FIG. 8Amay be carried out by a centralized processing device which has accessto the measurements taken by some or all of the PV devices (such as, asystem inverter including a processing unit, communicatively coupled tothe PV devices so that the devices may communicate their measurements tothe inverter).

Reference is now made to FIG. 8B, which illustrates different stages ofthe mapping algorithm depicted in FIG. 8A according to a certainillustrative embodiment. In this illustrative embodiment, forillustrative purposes, step 815 comprises two stages. The first stagemay include utilizing a mesh-relaxation technique, such as described in“Relaxation on a Mesh: a Formalism for Generalized Localization” by A.Howard, M. J. Mataric and G. Sukhatme (Proceedings of the IEEE/RSJInternational Conference on Intelligent Robots and Systems (IROS 2001)),with the result of the first stage being formulated as a Least-Squaresproblem and input to a Least-Squares solving method (many of which maybe found online, such as the “leastsq” method packaged in the SciPylibrary for the Python programming language). 870 depicts the reallayout of the PV installation, with each device numbered (0-119) andlocated in its “real” place. The real layout depicted in 870 is notknown to the algorithm at the time of running, and is provided here forillustrative purposes. 880 depicts an example result of step 800, wherethe mapping algorithm has generated random location estimates for eachdevice. In this illustrative embodiment. RSSI indicators (in conjunctionwith estimated random signal attenuation factors) are used to estimatepairwise distances between each pair of devices, and the estimates areinput to an implementation of the “Relaxation on a Mesh” methodmentioned above, at a first stage of step 815. The resultant ELM isdepicted in 890, which includes some misaligned rows and a few deviceswhich deviate from their “real” location illustrated in 870. Theestimate depicted in 890 may then be input to the SciPy “leastsq”function, and a final, smooth, accurate ELM may be output, such as theoutput depicted in 895. It should be noted that the diamond-like shapeof the ELM 895 is obtained because of unequally scaled X and Y axes. Forexample, when the axes in L4 were scaled equally, the shape may be thatof a rectangle, which may be similar to the real installation asillustrated in L1. In one implementation the ELM 895 illustrates anestimate at the end of step 815. In the example illustrated in FIG. 8B,the degree of symmetry present in the installation may reduce accuracyof the estimated layout. In certain instances, a PV installation mayinclude asymmetrical elements (such as some rows being shorter thanother, such as in the system depicted in FIG. 2B) which may improveaccuracy when matching ELM elements to NIM elements. In certaininstances, asymmetrical elements may result in improvements inalgorithmic convergence and accuracy.

Reference is now made to FIG. 9 , which shows an illustrative PVinstallation comprising PV devices which may be described on a map ofthe installation. The installation may include a plurality of PV strings916 a, 916 b, to 916 n. The PV strings may be connected in parallel.Each PV string 916 a-n may include a plurality of PV devices 903. PVdevices 903 may be PV cells or panels, power converters (such as DC/DCconverters or DC/AC converters) coupled to or embedded on PV panels,monitoring devices, sensors, safety devices (such as fuse boxes, RCDs),relays, and the like, or any combinations thereof. Individual PV devices903 may be identical or might be different. The PV devices 903 may becoupled in series or in parallel. For example, each PV device 903 maycomprise a DC/DC converter or DC/AC inverter coupled to a PV panel andconfigured to operate the panel at a set or determined power point, suchas a maximum power point. Each DC/DC or DC/AC converter may convertinput PV power to a low-voltage, high-current output, and multipleconverters may be serially connected to form a string having highvoltage. In some embodiments, each PV device 903 may include DC/DC orDC/AC converter converting input PV power to a high-voltage, low-currentoutput, and multiple converters may be connected in parallel to form astring having high current.

The plurality of PV strings 916 a-n, which may be connected in parallel,may be coupled to the inputs of PV system grouping device 904. In someembodiments. PV system grouping device 904 may comprise a centralinverter configured to convert a DC input to an AC output. The AC outputmay be coupled to a power grid. In some embodiments, PV system groupingdevice 904 may comprise one or more safety, monitoring and/orcommunication devices. Each of the PV devices 903 and/or the groupingdevice 904 may include an ID tag such as a barcode, serial number and/ormemory or RFID card, that comprises identifying information.

In illustrative embodiments, it may be possible to match device IDs tophysical locations on a map by utilizing various methods describedherein. In some embodiments, it may be possible to match device IDs tophysical locations on a map by determining which devices are coupledserially to one another (such as which devices comprise each string),determining the order of the various strings and then determining theorder of the devices within each string.

FIG. 10 is a flow diagram of a method for grouping power devices intogroups according to one or more illustrative aspects of the disclosure.In one or more embodiments, the method of FIG. 10 , or one or more stepsthereof, may be performed by one or more computing devices or entities.For example, portions of the method of FIG. 10 may be performed bycomponents of a computer system. The method of FIG. 10 , or one or moresteps thereof, may be embodied in computer-executable instructions thatare stored in a computer-readable medium, such as a non-transitorycomputer-readable medium. The steps in the method of FIG. 10 might notall be performed in the order specified and some steps may be omitted orchanged in order.

Reference is now made to FIG. 10 , which depicts a method for groupingPV devices into strings. The method may be used to determine whichdevices are serially connected to one another in systems such as thesystem depicted in FIG. 9 . The method of FIG. 10 , or one or more stepsthereof, may be used to group devices into map rows, such as at step 132of FIG. 2A. The method may apply to a plurality of PV devices which areable to change their output voltage, such as DC/DC converters, andreport their output parameters (such as voltage, current) to a systemmanagement unit communicatively coupled to some or all the PV devices.

At step 900, it may be determined that one or more power devices areungrouped. For example, initially, all power devices may be ungrouped.At step 910, a power device may be selected from the ungrouped powerdevices. The power device may be selected randomly. For example, anoptimizer, such as an optimizer coupled to a power generation source,may be selected. In one implementation, all or portions of step 910 maybe performed by an inverter. At step 920, the power device selected at910 may be instructed to decrease or increase an output voltage of thepower device. For example, a message may be sent to the power device,via PLC, wirelessly, or via other communications methods, to increase ordecrease the output voltage of the power device.

At step 930, the method may wait for power devices, such as ungroupedpower devices, to report operating points. For example, the powerdevices may send telemetries based on a schedule or at variousintervals. At step 940, operating points received from power devices,such as ungrouped power devices may be recorded. The operating pointsmay be responsive to the increase or decrease in output voltage that wasrequested at step 920.

At step 950, one or more devices that do not report a change in voltagemay be grouped with the power device selected at step 910. For example,devices that do not report a change in voltage greater than a thresholdchange in voltage may be grouped with the selected power device. Thethreshold may be preset or predetermined, or determined based onreceived operating points.

At step 960, it may be determined whether there are one or moreungrouped devices. When there are one or more ungrouped devices, themethod may return to step 910 and select one of the one or moreungrouped devices. Otherwise, when at step 960 it is determined that alldevices have been grouped, the method may proceed to step 970. At step970, the grouping may be considered complete, and the division ofdevices into groups may be output.

As an example of the method described in FIG. 10 , assume PV systemgrouping device 904 is an inverter including a power-line-communications(PLC) or wireless transceiver and a processor, and each PV device is anoptimizer including a DC/DC converter, a maximum-power-point-tracking(MPPT) circuit and a PLC or wireless transceiver. Each optimizer may becoupled to one or more power generation sources such as PV panels,batteries and/or wind turbines. Before the grouping process begins, eachoptimizer may be configured to output a certain low, safe voltage suchas 1V. Since the strings of optimizers (such as 316 a, 316 b) arecoupled in parallel, they may maintain a common voltage between the twoends of each string. The optimizers may periodically send telemetries tothe PV system grouping device 904 using PLC, where they report theircurrent output voltages. At step 900, the power devices (optimizers inthis example) are ungrouped. At step 910, the inverter chooses a firstoptimizer at random (such as Optimizer A, belonging to String F), and atstep 920 sends a message (via PLC or wirelessly) instructing Optimizer Ato increase its output DC voltage. This increase in voltage results in acorresponding increase in the voltage of the string including the chosenoptimizer. String F. To maintain a common string voltage, the optimizersbelonging to all the other strings may increase their voltages as well.However, the optimizers which are part of String F (such as OptimizersB-K) might not increase their output voltage, as Optimizer A has alreadyraised its voltage. When the optimizers next send telemetries to theinverter, via PLC or wirelessly, at step 930. Optimizer A may report ahigh voltage, Optimizers B-K may report the same voltage as before, andall other optimizers may report increases in voltage. At step 940, theinverter processor may record the reports from all the optimizers. Atstep 950, the inverter may determine that all optimizers not reporting asignificant change in voltage (B-K) belong to the same string as theoriginally selected optimizer (A), group them as a string and removethem from the “ungrouped power devices pool”. The algorithm then repeatssteps 910-50 until all optimizers have been grouped, at which stage itcomes to an end, at step 970 outputting the division of optimizers intogroups.

Reference is now made to FIG. 11A, which shows an illustrativeembodiment of a PV string of PV devices, where it may be possible todetermine the order of the devices within the string. Time DomainReflectometry (TDR) may be used to determine the ordering of PV deviceswithin a PV string. String 317 may comprise a plurality ofserially-connected PV devices 104, such as PV devices 104 a, 104 b, to104 k. The string 317 may comprise any number of PV devices 104 a-k.Devices 104 a-k may comprise elements similar to those previouslydiscussed with regard to PV devices 103. Devices 104 a-k may eachinclude power converter 210 (such as a DC/DC or DC/AC converter) whichreceives input from a PV panel, battery or other form of energygeneration, and produces an output. One output of converter 210 may becoupled to a variable impedance Z 270, and the other output may serve asthe device output, to be coupled to an adjacent PV device in string 317.In this manner, string 317 may include a plurality of variableimpedances which are coupled to the cables which couple the PV devicesto one another, forming the serial string. Each PV device 104 a-k mayinclude a controller 220, configured to control the value of variableimpedance Z 270. Controller 220 may be the same controller used tocontrol the other components of PV device 104 a-k (such as powerconverter 210, communication module 230, safety device(s) 240, auxiliarypower 250, and/or the like), or it may be a different controller.Transceiver 115 may be coupled to the string 317, and may be configuredto inject a voltage or current pulse over the string and measure thereflected wave. The transceiver may be coupled to one of the edges ofthe string, or may be coupled to a middle point between two devices.According to TDR theory, the waveform reflected back to the transceiverdepends on the characteristic impedance of the PV string line. Thecharacteristic impedance of the PV string may be affected by each ofvariable impedances 270 coupled to it, so by rapidly changing variableimpedance Z 270 on one of the serially connected PV devices, a rapidlychanging reflected waveform may be formed.

PV devices may have integrated receivers, transmitters, or transceivers260 in each device, which may allow transmitting or receiving an RFsignal on the PV conductors to determine the order of the PC deviceswithin the string of PV panels. A transceiver signal may be fed tocommunication module 230 for interpreting a PLC communication, measuringa signal parameter, and/or the like. The wavelength of the signal may beshorter than the length of the conductors in PV systems, and theimpedance components along the way may respond by limiting transmissionat some frequencies across the conductors and nodes. Devices connectedat various nodes along the string (node devices) along the string may bea power device such as a PV device, a PV power device, an inverter, anoptimizer, a junction box, a combiner box, a bypass diode circuit, adirect-current (DC) to alternating-current (AC) power inverter, a DC toDC power converter, a micro-inverter, a photovoltaic panel circuit, aconnector embedded circuit, or other energy management devices, wherethe device may comprise a signal receiver and/or transmitter and aserial impedance modification circuit as in the drawings. For example,any one or more of the above power devices may comprise an impedancemodifying circuit on one or more of the output connectors of the powerdevice.

Devices 104 a-k, such as PV device 104, may further incorporate a PLCfilter 280, ground (GND) switch 290, and/or the like. PLC filter 280 maybe a wave trap filter, a band stop filter, a notch filter, and/or thelike, and attenuate the PLC communication signal during propagation onthe power device string. When the PLC filter is activated. GND switch290 may be closed so that a return loop is created through the groundswitch. In this manner, the first power device in the series may beidentified, then PLC filter 280 is disconnected and GND switch 290 isopened for the first power device, and then process continued down thestring until the order of the power devices in the string is determined.

The electrical signal may also be sent from one power device to anadjacent power device, and the phase may be measured. For example, whenthe wavelength is set to a value that is four times the string length,and the phase of the signal is adjusted and referenced so that the firstpower device is at zero phase, then the other power devices in thestring may have a monotonically increasing or decreasing phase value,and thus the order of the power devices along the string may bedetermined by the phase values. For example, 20 power devices areconnected with a 2-meter conductor between power devices (40 meterstotal), and the electrical signal is initiated by the first power devicewith a wavelength of 50 meters (1.5 MHz), whereby each power device maysee an increasing phase of 14.4 degrees. For example, the first powerdevice may measure a 14.4-degree phase shift, the second power devicemay measure a 28.8-degree phase shift, and the like. For example, for astring of n power devices, each with a distance of x; between them(where i denotes the index of the PV device) and a signal wavelength of□i, the signal phase that will develop between device i-1 and device iis 360*x_(i)/□i degrees. So the formula for the phase at each device is:p_(i)=Σ_(k=0) ^(i)360*X_(k)/λ_(k)

When one of the node devices transmits an electric signal along thestring of serially connected devices, the signal strength at each nodemay be measured and the measured value may be analyzed to determine theorder of the devices along the string. For example, by setting one ofthe node devices to have a different impedance compared to the others,it may be determined which of the nodes are proximal to the node withthe different impedance and which are distal. By iteratively changingthe impedance of one node device after the other (such as changing andreverting impedances), the measured values may be analyzed to determinethe order of the devices. Thus, based on the determined order of thedevices, when one of the devices has a malfunction or needs maintenance,a notification may include the location of the device along the string,thereby assisting the repair/maintenance of one or more of the devices.

For example, a power device at the end of the string may transmit thesignal and the power devices further down the string may recordmeasurements of the signal. As another example, a power device at themiddle of the string sends a signal on one or more of the outputconnectors of that power device, and the other devices on the portion ofthe string connected to that power device record measurements of thesignal. The measurements may be sent to a central processor, such as aprocessor of one of the devices for analyzing to determine the order ofthe power devices on the string.

When two or more parallel string strings are connected to a common powerdevice, such as an inverter, and the end power device sends the signalto an output connector, the devices on all the parallel strings mayrespond and send back the measured values. To separate measured valuesfrom each string, the processor may use the groups of power devices thathave been classified by strings using the methods described herein. Forexample, the inverter may simultaneously detect the order of powerdevices on multiple parallel strings by segregating the measurementvalues according to the string they belong to.

Reference is now made to FIG. 11B, which shows several examples ofvariable impedance configurations. Variable impedance 1110 may includeinductor L1, resistor R1, capacitor C1 and switch Q1 (such as a MOSFET),all connected in parallel. Inductor L1, resistor R1, capacitor C1,and/or other components may comprise a variable impedance, a computerdetermined impedance, and/or the like. For example, the impedance isvaried during a spread spectrum reflectometry or refractometry detectionmethod. For example, in a refractory technique each power device mayattenuate the transmission line electrical signal, and thus the signalamplitude may be used to determine the relative order of the powerdevices. When switch Q1 is ON (such as by a controller applying anappropriate voltage to the gate of MOSFET) the total impedance ofimpedance 1110 may be zero, since the switch bypasses the otherimpedance elements. When switch Q1 is off, the impedance of 1110 may benonzero, and may be calculated as the impedance of the other threecomponents connected in parallel. Variable impedance 1120 may compriseinductor L2, resistor R2, capacitor C2 connected in parallel, inductorL22 coupled to them in series, and switch Q2 connected in parallel tothe whole arrangement.

Here, when Q2 is ON the equivalent impedance of 1120 may be zero, andwhen it is OFF the impedance of 1120 may be nonzero, and calculated asthe impedance of R2. C2 and L2 in parallel added to the impedance ofL22. Variable impedance 1130 features two switches, Q3 and Q33, and morethan two impedance levels. When Q3 is ON, the impedance of 1130 is zero.When Q3 and Q33 are both OFF, the impedance of 1130 is simply theimpedance of inductor L3. When Q3 is OFF and Q33 is ON, the impedance of1130 is the equivalent impedance of inductor L3, resistor R3 andcapacitor C3 all coupled in parallel. Obviously, many more arrangementsof components may be utilized for different (or additional) impedancelevels. The switching of the switches (Q1, Q2, Q3, Q33) may becontrolled by an appropriate controller (such as DSP, MCU. FPGA and/orthe like) within the relevant PV device.

Reference is now made to FIG. 11C, which shows a schematic ofillustrative conductor networks according to one or more illustrativeaspects of the disclosure. A RF pulse or wave may be transmitted fromone location of a series network of transmission lines and received atother locations along the series. When the wavelength is near to orsmaller than the conductor lengths, the impedances along the conductormay affect the wave propagation, such as a transmission line effect. Forexample, the signal or wave may propagate through the network, and bedetectible at power devices along the network, such as OPT A, OPT B, OPTC, and/or the like. The power devices may be configured to set or adjustan impedance at each node of the network, and the set impedance at thepower devices may be responsive to the cable impedances, denoted asLcable. For example, each power device may include an impedanceswitching circuit, an impedance setting circuit, an impedance circuit,an impedance masking circuit, and/or the like. Each power device mayinclude a receiver configured to receive the RF pulse or wave, andrecord the wave received at the device. The recorded wave strengths ateach device (or node) may be transferred to a central device forprocessing, including comparing the recorded waves when different powerdevices are set to different combinations of impedances. The analysis ofthe waves and/or the commands to set impedance values may be used todetermine the order of the power devices along the network length.

Reference is now made to FIG. 11D, which shows a schematic ofillustrative second conductor networks according to one or moreillustrative aspects of the disclosure. An inverter that produces an ACoutput power is connected to a DC power source using terminals DC+ andDC−. Each power device Opt_1. Opt_2, and Opt_n, may comprise impedancessuch as Cout. Ccomm, Lcomm, and/or the like. The parasitic leakagecapacitance Llk1, Llk2, Llkn and the like may be used together with theimpedances of the devices to measure a RF pulse or wave generated by theinverter, and the signal amplitude may be used to determine the orderingof the power devices based on the recorded RF wave or pulse at eachpower device. The phase, timing and known location of the elements maybe used to determine or analyze the of ordering of devices along thestring. For example, the leakage current 1117 from the parasiticcapacitances to ground may be used to analyze the recorded waves. Aresistor, denoted Rmatched, may be connected from DC+ to ground, eitherin series or parallel to a capacitor.

The impedance adjusting circuit of the power devices may be used toidentify the neighboring power devices using a peer-to-peer typehandshaking technique. For example, an electrical signal is transmittedfrom one power device, and the other power devices dynamically changetheir impedance (such as changing and reverting the impedance) until itis determined which of the other power devices in neighboring to thetransmitting device. For example, a PLC communication module is used tocommunicate an electrical signal between two of the power devices, andthe other power devices sequentially and/or alternately implement animpedance change using their impedance adjusting circuit, such as a highimpedance, and the power devices that caused a communication errorbetween the two communicating power devices are determined to be orderedin the serial string in between the two communicating power devices. Bychanging the selected two communicating power devices and repeating thedetermination of the intermediate power devices between them, the orderof multiple power devices in each of the multiple parallel strings maybe determined.

The transmitting of electrical signals may be performed simultaneouslybetween multiple devices, such as each device transmitting at a slightlydifferent frequency (such as between a 10 Hz to 100 MHz frequencydifference), and the resulting recorded signal values at each powerdevice may be used (such as after applying a Fourier-transform) tosimultaneously determine the relative signal strength received at eachpower device and thus the order of the power devices. In some aspects,not all of the power devices need to record the signal and it may besufficient to determine the order of all power devices from a subset ofpower devices that record the signals.

The impedance used for PLC communication may be adjusted to preventeffective PLC communication between power devices and thereby determinethe order of power devices, the string of a power device in parallelstrings, and/or the like. For example, when a power device in one stringchanges its impedance such that the PLC communication in that string isno longer possible (such as where the power devices creates a largeseries impedance rendering PLC communications ineffective due tosignificant signal attenuation by the large series impedance), the otherpower devices of that string may not be able to effectively communicatewith a central power device and the power devices belonging to thatstring are determined. For example, commanding another power device toadjust impedance that is not from the first string may result in thepower devices in the second string from not communicating effectivelywith the central power device. For example, by repeating this technique,the power devices may be categorized into strings.

A switch in each power device may connect the PLC communication loop toground, and an impedance filter in each power device may prevent theelectrical PLC signal form passing to the next power device in thestring. By applying all of the impedance filters, setting the switch toconnect the power device PLC communication loop to ground in one powerdevice, and selectively setting the switch to connect the power devicePLC communication loop to ground in another power device, the adjacentpower device in the string may be located.

For example, under normal operating conditions in a solar powergeneration system, a PLC communication may be passed between powerdevices using the solar power connectors, which form a loop, such as astring of power devices connected at both ends to a central powerdevice, such as an inverter. In a normal operating mode, the loop is notconnected to ground. During a system installation, when the powerdevices are connected in a serial string to each other but no power isproduced by the system, the central power device may command powerdevices to set a filter that prevents the PLC communication from passingalong the loop. The central power device may then sequentially commandeach power device in turn to connect to ground, and when a PLCcommunication signal is received at the central power device, the powerdevice that sent the signal may be the first power device in the string.The central power device may then command sequentially another powerdevice to connect to ground, and when a communication link isestablished determine that the power device last connected is the secondpower device in the string. Similarly, the central power device mayiteratively determine the order of the power devices in the stringaccordingly.

Reference is now made to FIG. 12A, which shows a waveform reflected froma PV string including variable impedances, according to illustrativeembodiments described herein. When illustrative variable impedances areswitched at a very high frequency, such as a frequency above 100kilohertz (kHz), such as hundreds of KHz, several megahertz (MHz), tensor hundreds of megahertz, or several gigahertz (GHz), a ripple may bedetected on the wave reflected back to the transceiver. When severalvariable impedances are varied on the same string, the ripple eachimpedance causes may appear at a different time, due to the differencein distance between impedances. For example, when two PV devicesincluding variable loads are spaced 1.5 meters (m) apart, with one ofthe PV devices being 1.5 meters closer to the transceiver than theother, the waveform transmitted by the transceiver may travel anadditional 1.5 meters to reach the further PV device, and the reflectedwave may travel an additional 1.5 meters as well on the way back, for atotal difference of 3 meters in the route. Assuming the waveforms travelat the speed of light, C=3·10⁸ m/sec. the ripple caused by the farthervariable impedance may appear

${\Delta t} = {\frac{3\lbrack m\rbrack}{3 \cdot {10^{8}\left\lbrack \frac{m}{s{ec}} \right\rbrack}} = {10{nanoseconds}({ns})}}$

later than the ripple caused by the closer variable impedance.

At other distances, the timing may change, such as from 1 meter to 100meters, corresponding to approximately 3 to 300 ns transit time. Thesignal frequency, conductor length, node impedances, and/or the like maydetermine (at least in part) the signal response characteristics of thepower device network. When multiple transceivers and/or receivers maymonitor the signals on the network the ordering of the devices on aserial network may be determined, as well as other parameters such asthe node impedances, the electrical conductor lengths, and/or the like.High-quality digital or analog sensors may be able to detect timedifferences at this resolution. For example, when transceiver 115commands device 104 b to vary its impedance, it may detect a rippleappearing on the reflected waveform after 200 ns. When transceiver 115commands device 104 a to vary its impedance, and it detects a rippleappearing on the reflecting waveform after 210 ns, it may determine thatdevice 104 a is 1.5 m further than device 104 b. By iteratively sendingsimilar commands to each device in the system, the transceiver unit maybe able to determine the relative distances of each PV device, and inconjunction with grouping the devices into strings and/or rows (usingmethods such as the illustrative embodiments shown in FIG. 10 ), thelocation of each device may be determined.

A signal transceiver or transmitter at a device that is electricallyconnected to the PV string may transmit a signal, such as aradiofrequency (RF) pulse. As the signal travels along the PV string,such as along a transmission line, the signal may be attenuated by eachpower device or power converter along the PV string (such as accordingto the impedances at each device). When the power devices measure thesignal that reaches them, and transmit the signal values to a centralprocessor, the recorded signals may be compared to determine the orderof the power converters along the PV string. For example, each powerconverter may have a small impedance that attenuates the signal by 10%,and the signals recorded at each power converter may be compared todetermine the location of each converter along the PV string.

To detect the transmitted signal at each PV power device, the signalreaching each power device is recorded by a receiver located in thepower device. The power devices may have a constant impedance, or amultiple impedance switching circuit that may configure one or moreoutput conductor of the power device to a different impedance state,such as a low impedance state, a high impedance state, a short circuitstate, an open circuit state, a mid-impedance, and/or the like. Forexample, an impedance switching circuit may configure one of the outputconductors to an impedance of zero ohms (a short circuit). 1 ohm. 2ohms. 5 ohms. 7 ohms, 10 ohms, 15 ohms, between 0.001 ohm and 5,000ohms, between 10 ohms and 1000 ohms, between 50 ohms and 500 ohms, lessthan 5,000 ohms, and/or the like. Here, as elsewhere in the description,ranges may be combined to form larger ranges.

Performing signal transmissions and recording of a signal at each powerdevice, when the impedance configurations of the devices are changed,allows detecting (such as determining) the order of the power devices.For example, when all impedances are the same and a leakage impedancefrom each panel to ground allows ordering the power devices by signalstrength, signal power, signal frequencies, and/or the like. Forexample, the leakage path through the chassis and parasitic capacitancemay change the signal path flow and thus the recorded signal amplitudeat each power device is proportional to the order of the power devicesin the string.

For example, when a first power device is providing a low impedance(such as a short circuit) and the others are providing high impedance,and the device providing a low impedance is switched from one device toanother until the order is determined. For example, when one powerdevice is providing a high impedance and the others are providing a lowimpedance, and the device with a short circuit is switched among thedevices in the string until the order is determined.

The receiver may be part of a transceiver, and each power deviceperforms a transmission and recording of the transmitted signals. Forexample, each power device transmits a slightly different signal, suchas different in phase, frequency, signal shape, signal harmonic content,and/or the like. The signal propagation in the serial conductor may bebetween 5 and 50 nano-seconds (ns) from one power device to the next, orfrom the transceiver to the power device, depending on the length ofconductor between the two nodes. For example, the distance is 4.5 metersand the signal propagates from one of the two nodes to the other of thetwo nodes within 15 ns. In this manner, the order of the power devicesin the string may be detected.

A signal change may be detected differentially, such as by comparingsignal attenuation between two or more states. For example, a signal ismeasured at each power device during a first impedance configurationamong the devices, and after one or more devices change the impedance,the signal is measured again, and the difference between the measuredvalues allows determining the order of the devices at least in part.

For example, one power converter has a high impedance and the otherconverters have a low impedance, and the power converters between thetransceiver and the high impedance converter may record a high signaland the ones on the other side may have a low signal. By changing theimpedance of each power converter one at a time, it may be possible todetermine the order of the power converters. Similarly, when all powerconverters except one have a middle to high impedance, the signals arerecorded at each converter, and the low impedance converter is changed(such as reverting to the previous impedance) until the order of thepower converters is determined by comparing the recorded signals.

Reference is now made to FIG. 12B, which shows an illustrative form of afirst wave received at devices along a transmission line according toone or more illustrative aspects of the disclosure. FIG. 12B shows thesignal generated from a transceiver 115 as received at each of 6 powerconverters, where the 4^(th) power converter has a high impedance. Thepower converters between transceiver 115 and the 4^(th) power device,such as the 1^(st), 2^(nd), and 3^(rd) devices, may record a high signalstrength and the 4^(th) power device and the ones after, such as the5^(th) and 6^(th) devices, may record a low signal. The high impedancecircuit may be located after the signal recorder on each device, and insuch a configuration the power converter having the high impedance mayrecord a high signal.

Reference is now made to FIG. 12C, which shows an illustrative form of asecond wave received at devices along a transmission line according toone or more illustrative aspects of the disclosure. For example, signalattenuation due to leakage may be detected with a signal attenuation ofan RF signal received and detected at each power device, such as anoptimizer. The natural impedance due to the leakage circuits may bedetectable at certain transmission line frequencies.

Reference is now made to FIG. 12D, which shows an illustrative form of athird wave received at devices along a transmission line according toone or more illustrative aspects of the disclosure. For example, alow-impedance (such as a short circuit) based PV panel locating methodmay lower the impedance of the power device connected to the PV panel,and the resulting signal changes may show that the power device with lowimpedance has a lower signal detected at that PV panel node. Forexample, a first configuration of impedances has inductance of L=10micro-Henry and capacitance of C=25 pico-farad so the resonancefrequency is approximately

$f_{c} = {\frac{1}{2\pi\sqrt{LC}} = {10{{MHz}.}}}$

The second configuration is close to a short circuit or a resistance ofzero. By sequentially modifying only one of the power devices to a lowimpedance, maintaining the other power devices at a high impedance mayallow detecting the location of each PV panel in the string.

The frequency of the transmitted signal and the impedance changes ateach device may be set so that the results of the signal measurementvalues at each node may be used to determine the order of the powerdevices in the string. For example, a spread spectrum frequency sweepsignal may detect aspects of the PV panel serial order. For example, asignal with a frequency of between 1 KHz and 10 MHz may be used. Forexample, a signal with a frequency of between 50 KHz and 50 MHz may beused. For example, a signal is used that has a frequency of 5 KHz, 10KHz. 15 KHz, 20 KHz, 25 KHz, 40 KHz, 50 KHz, 100 KHz, 200 KHz. 500 KHz,1 MHz, 5 MHz, 10 MHz. 20 MHz, 50 MHz, 100 MHz. 200 MHz. or the like. Forexample, a signal is used that has a very low frequency (VLF), a lowfrequency (LF), a medium frequency (MF), a high frequency (HF), or avery high frequency (VHF).

Reference is now made to FIG. 12E, which shows an illustrative plot ofsignals received at devices along a transmission line according to oneor more illustrative aspects of the disclosure. A first plot 1201 showsthe signals recorded at different nodes when the impedance is set tozero at each—such as a short circuit impedance where the signals are atfull strength. A second and third plots 1202 and 1203 show a slightlyattenuated signal and zero signal from an open circuit respectively. Afourth and fifth plots 1204 and 1205 show a slightly attenuated signaland slightly elevated signal from power devices with intermediateimpedances, respectively.

Reference is now made to FIG. 13 , which shows a flow diagram of amethod for testing power devices according to one or more illustrativeaspects of the disclosure. In one or more embodiments, the method ofFIG. 13 , or one or more steps thereof, may be performed by one or morecomputing devices or entities. For example, portions of the method ofFIG. 13 may be performed by components of a computer system. The methodof FIG. 13 , or one or more steps thereof, may be embodied incomputer-executable instructions that are stored in a computer-readablemedium, such as a non-transitory computer-readable medium. The steps inthe method of FIG. 13 might not all be performed in the order specifiedand some steps may be omitted or changed in order.

The method of FIG. 13 may be used to determine the relative distances ofserially connected PV devices from a waveform-generating transceiver, ina system which may be arranged similarly to the system shown in FIG.11A. At step 1320, one or more power devices may be defined as“untested”, such as they have not been commanded to vary theirimpedance. For example, initially, all power devices may be determinedto be untested.

At step 1325, one of the untested devices is selected. For example, anuntested device may be selected randomly at step 1325. At step 1330, thedevice selected at step 1325 may be commanded to vary its variableimpedance. For example, the device may be commanded to vary its variableimpedance at a determined frequency, such as a high frequency. At step1335, a transceiver may transmit a voltage pulse over the PV string. Atstep 1340, the transceiver may receive the reflected wave, record and/ortime the response, and save the received or determined data to memory atstep 1345. At step 1350, the selected device may be removed from thepool of “untested” devices, and may be commanded, for example, by thetransceiver, to stop varying its output. At step 1355, the transceivermay check or determine when there are devices in the string which areuntested. When there are untested devices, the method may return to step1325, and another power device may be selected. When it is determined,at step 1355, that all power devices have been tested (that is, nountested devices remain), the method may proceed to step 1360. At step1360 the transceiver (or a master control unit or other system whichreceives data from the transceiver) may analyze the saved reflectedwaveforms and time samples, determine (as explained previously) whichdevices are closer than others, and estimate the distances betweendevices.

Reference is now made to FIG. 14 , which shows an illustrative PVarrangement. In PV arrangement 309, PV devices 105 a, 105 b, to 105 kare coupled in parallel to one another. Although not illustrated in FIG.14 , the devices 105 a-k may be coupled in parallel to a system powerdevice such as an inverter, management and/or communication unit, safetydevice(s), or other devices. Each PV device 105 a-k may be coupled to apower source (such as a PV panel, a battery, a wind turbine, and/or thelike) and may include a DC/DC or DC/AC converter configured to output ahigh-voltage DC or AC voltage which is common to all PV devices 105 a-kcoupled in parallel. In this illustrative system, devices 105 a-k mightnot be coupled in series with one another. Transceiver 116 may becoupled to the PV devices 105 a-k and may be configured to communicatewith the devices 105 a-k. It may be desirable for the system installerto know the distances between the various devices and the transceiver,or to know the distance ordering (such as which device 105 a-k isclosest, which is the farthest, and/or the like). In parallel-connectedembodiments, a voltage or current pulse may be transmitted, with the PVdevices 105 a-k taking turns varying their impedance as instructed bythe transceiver 116, as explained above in regards to FIGS. 11A-14 . Inthis embodiment, the transceiver 116 may analyze the current returningwave for disturbances caused by the varying impedance circuits, andbased on the time delay in recording caused by each PV device, determineand/or list the devices 105 a-k in order of distance from thetransceiver 116.

Reference is now made to FIG. 15A, which depicts a PV device accordingto illustrative embodiments. PV panel 106 may include one or more solarcells on one side (not explicitly shown), and a lower portion of ajunction box 152 on a second side. A plurality of panel conductors 153such as ribbon wires may be coupled to the PV cells on one side of thepanel, and may protrude through slots in the lower junction box portion152 on the other side. The lower junction box portion 152 may befastened to the PV panel 106 at the time of manufacturing. Anidentification label (ID label) 151 may be attached to the panel 106 orlower junction box portion 152 either at the time of manufacturing orthereafter. The ID label 151 may be a barcode, serial number. RFID tag,memory device or any other medium for containing information that may beread by an external device. An upper junction box portion 150 may bemechanically attachable to the lower junction box portion, and mayinclude electronic circuits configured to receive PV power from theconductors 153, and may include string conductors 154 for coupling theupper portion to adjacent PV devices. In some embodiments, the upperjunction box portion 150 may be coupled to other upper box portions atthe time of manufacturing, using conductors of appropriate length toallow a plurality of upper portions 150 to be attached to a plurality oflower junction box portions during deployment in a PV installation. Theupper junction box portion 150 may include an appropriate device forreading the ID label 151 from the panel or lower junction box portion.For example, when the ID label 151 includes a barcode, the upper portion150 may include a barcode scanner. When the ID label 151 includes aserial number, the upper portion 150 may include a camera and be coupledto a device configured to identify digits and/or letters. The upperportion 150 may include an RFID tag reader, or a device configured toread identifying information from a memory device. The upper portion 150may read, process and/or communicate the ID information automaticallywhen attached to the lower junction box portion 152. The upper junctionbox portion 150 may also be configured with its own ID information, andbe able to communicate to a management device both its own ID tag andthe ID label of the PV panel it is coupled to.

PV device ID tags may be used for several purposes. In some embodiments,the ID tags may be used to create a map of the PV installation includingthe locations of specific devices in the installation. In someembodiments, the tags may be used to authenticate PV devices and ensurethat approved devices are used in the installation, for example, byusing an authentication protocol. In some embodiments, the protocol maybe carried out by circuits and/or devices comprised in the upper part ofthe junction box. In some embodiments, the ID tag may be communicated toan external management device, and an authentication protocol may becarried out between components included in the lower portion, the upperportion and an external device or management unit.

Reference is now made to FIG. 15B, which shows an illustrativeembodiment of an upper portion of a junction box, such as the one thatmay be used in the arrangement depicted in FIG. 15A. Upper junction boxportion 150 may comprise power converter 245, which may be configured toreceive DC power from a PV panel and convert it to DC or AC power at theconverter outputs. Upper junction box portion 150 may comprise variableload 275. Upper junction box portion 150 may comprise an ID reader 285.Upper junction box portion 150 may further comprise controller 270 suchas a microprocessor. Digital Signal Processor (DSP) and/or an FPGA,configured to control some or all of the other functional blocks. Insome embodiments, the controller may be split into multiple controlunits, each configured to control one or more of the functional blocksof upper portion 150. Upper junction box portion 150 may compriseMaximum Power Point Tracking (MPPT) circuit 295, which may be configuredto extract power, such as a maximized power, from the PV module theupper portion 150 is coupled to. In some embodiments, controller 270 mayinclude MPPT functionality, and thus MPPT circuit 295 may not beincluded in the upper portion 150. Controller 270 may control and/orcommunicate with other elements over common bus 290. In someembodiments, the upper junction box portion may include circuitry and/orsensors 280 configured to measure parameters on or near a PV module orjunction box, such as voltage, current, power, irradiance and/ortemperature. In some embodiments, the upper junction box may includecommunication device 255, configured to transmit and/or receive dataand/or commands from other devices. Communication device 255 maycommunicate using Power Line Communication (PLC) technology, or wirelesstechnologies such as ZigBee, Wi-Fi. Bluetooth, cellular communication orother wireless methods. In some embodiments, the upper junction boxportion may include safety devices 260 (such as fuses, circuit breakersand Residual Current Detectors). The various components included inupper junction box portion 150 may communicate and/or share data overcommon bus 290.

FIG. 16 is a flow diagram of a method for grouping power devices intostrings. The method may be used to determine which devices are seriallyconnected to one another in systems such as the system depicted in FIG.9 . The method of FIG. 16 , or one or more steps thereof, may be used togroup devices into map rows, such as at step 132 of FIG. 2A. The methodmay apply to a plurality of power devices which are able to report theiroutput parameters (such as voltage, current) to a system management unitcommunicatively coupled to some or all of the power devices. Accordingto Kirchhoffrs Current Law (KCL), serially coupled devices carry thesame current. According to KCL, when a plurality of serially-coupledpower devices repeatedly report their output current to a systemmanagement unit at substantially simultaneous times, the reportedcurrents may be substantially the same in magnitude. By logging thereported currents over a period of time, it may be determined whichpower devices are unlikely to be serially coupled to one another (suchas when two devices report currents which are significantly different atsubstantially the same time, they are likely not serially coupled) andby a process of elimination and application of an appropriate stoppingcondition, an accurate estimate of the arrangement of power devices in aPV system may be obtained.

At step 160, initial grouping possibilities may be considered. Forexample, each power device may be considered to be “possibly paired” toeach other power device in the system. In some embodiments, morelimiting initial possibilities may be considered based on priorknowledge. For example, it may be known that two power devices are notserially coupled to one another, and they may be initially considered“not paired.” In some embodiments, a counter may be optionally set totrack the number of iterations the method has run. At step 161, themethod may receive current measurements from two or more power devicesat substantially the same time.

At step 162, some of the current measurements may be compared to oneanother. For example, when Device A and Device B are considered“possibly paired” at step 162 of the method, the current measurements ofDevice A and Device B. I_(A) and I_(B), respectively, may be compared toeach other. When the current measurements are not substantially thesame, the estimated relationship between Device A and Device B may bechanged to “not paired.” in some embodiments, more than one instance ofsubstantially different currents may be required to change an estimatedrelationship to “not paired.” For example. Device A and Device B may beconsidered “possibly paired” until three pairs of substantiallydifferent current measurements have been reported. In some embodiments,the determination of whether currents are substantially the same isbased on an absolute current difference. For example, when|I_(A)_I_(B)|<ϵ for an appropriate ϵ (such as 10 mA, or 100 mA, or 1A),then I_(A) and I_(B) might be considered “substantially the same.” Insome embodiments, the determination of whether currents aresubstantially the same is based on a relative current difference. Forexample, when

$\frac{❘{I_{A} - I_{B}}❘}{I_{B}} < {\alpha{and}\frac{❘{I_{A} - I_{B}}❘}{I_{A}}} < \alpha$

for an appropriate α (such as 0.01, or 0.03, or 0.1) then I_(A) andI_(B) might be considered substantially the same. In some embodiments,multiple criteria may be used to determine when two currents aresubstantially the same.

By comparing pairs of current measurements to each other as detailedabove, it may be determined which devices are unlikely to be seriallycoupled to one another. In some embodiments, the method may comparecurrent measurements of each pair of power devices considered “possiblypaired,” and based on the result of the comparison, the method maychange the relationship between the pair of power devices to “notpaired.” In some embodiments, the method may compare only a portion ofthe current measurements to one another. In some embodiments, some orall the current measurements selected for comparison may be chosen atrandom.

At step 163, the method determines when a stop condition has beenreached. In some embodiments, a stop condition may be reached when acertain number of iterations have been completed. The number ofiterations which trigger the stop condition may be fixed (such as 10,50, or 100), or may depend on the number of power devices in the system(such as N/10. N/2 or √{square root over (N)} for a system containing Npower devices). In some embodiments, the stop condition may be triggeredwhen a certain number of iterations have not changed the relationshipbetween any two power devices. For example, when three method iterationshave not changed the relationship between any two devices to “notpaired,” the stop condition may be reached. In some embodiments, thestop condition may be reached when each power device is considered“possibly paired” to no more than a certain number of other devices. Forexample, a stop condition may be reached when each power device isconsidered “possibly paired” to no more than twenty devices, or fortydevices, or sixty devices. In some embodiments, a stop condition isreached based on a combination of criteria. For example, a stopcondition may be reached only when three method iterations have notchanged the relationship between any two devices to “not paired,” andadditionally, each power device is considered “possibly paired” to nomore than fifty devices.

When the method determines that the stop condition has not been reached,at step 165 the iteration counter may be incremented, and the method mayreturn to step 161. When the method determines that the stop conditionhas been reached, the method may continue to step 164, and for eachPower Device X, output the group of power devices that are considered“possibly paired” to Power Device X (such as the “potential group” ofPower Device X).

Reference is now made to FIG. 17A, which shows an illustrativeembodiment of a PV string of PV devices, where it may be possible todetermine the order of the devices within the string. Selective couplingof PV devices to a common ground may result in leakage current, whichmay be used to determine the ordering of PV devices within a PV string.String 318 may comprise a plurality of serially-connected PV devices107, such as PV devices 107 a, 107 b, to 107 k. The string 318 maycomprise any number of PV devices 104 a-k. The string may be coupledbetween a ground terminal and a power bus. The voltage between theterminals of each PV device may vary from device to device. For example,in the illustrative embodiment depicted in FIG. 17A, PV device 107 aoutputs 25V. PV device 107 b outputs 30V (55V-25V=30V), and PV device107 k outputs 39.3V (700-660.7V=39.3V). The string voltage may be thesum of the voltages output by each PV device in the string, with thepower bus being at voltage approximately equal to the string voltage.

Devices 104 a-k may comprise elements similar to those previouslydiscussed with regard to PV devices 103 and/or 104. Some elements havenot been explicitly illustrated. Devices 104 a-k may each include powerconverter 211 (such as a DC/DC or DC/AC converter) which receives inputfrom a PV panel, battery or other form of energy generation, andproduces an output. The converter may include two output terminals forserial coupling to adjacent PV devices in string 318. One output ofconverter 211 may further be coupled to a leakage circuit 108 at leakageterminal LT. Leakage circuit 108 may be variously configured. In anillustrative embodiment such as shown in FIG. 17A, leakage circuit 108may comprise a serial branch including resistor R, switch Q andcurrent-sensor A1. The serial branch may be coupled to a commonelectrical ground. In some PV installations, the mounting structuresused to support PV panels may be required to be coupled to a commonground, and in such embodiments, the leakage branch may be coupled tothe ground via the mounting structures. In some embodiments, alternativegrounding points may be considered. Resistor R may be of largeresistance, such as 10 kΩ, 100 kΩ or even 1 MΩ or larger. Switch Q maybe implemented using an appropriate device such as a MOSFET. Duringregular operating conditions, switch Q may be in the OFF position,disconnecting leakage terminal LT from the grounding point. Switch Q maybe temporarily switched to ON, allowing current to flow from the leakageterminal LT to the ground. In some embodiments, where switch Q andcurrent sensor A1 may have negligible resistance, a current of magnitudeapproximately proportional to the voltage at leakage terminal LT mayflow through the leakage circuit and be sensed by current sensor A1. Forexample, when the voltage at leakage terminal LT is 100V, and theresistor R is of resistance 100 kΩ, current sensor A1 may sense aleakage current of

$\frac{100V}{100k\Omega} = {1{{mA}.}}$

In some embodiments, PV device 107 may include a communication devicefor transmitting leakage current measurements to a management deviceconfigured to use the current measurements for appropriate calculations(not illustrated explicitly). Controller 214 may be similar tocontroller 220 described with regard to FIG. 11A, and may further beconfigured to control the switching of switch Q. In some embodiments, aseparate controller may be dedicated to switching switch Q.Communication device 212 may be configured to communicate with othersystem power devices for sending or receiving commands or data. Forexample, communication device 212 may be configured to providemeasurements of a voltage or current at leakage terminal LT.Communication device 212 may be a wireless (such as a cellular, ZigBee™,Wi-Fi™, Bluetooth™ or other wireless protocol) transceiver, or a wiredcommunication device (for example, a device using Power LineCommunications).

Returning to string 318, in some embodiments each PV device 107 maycomprise a leakage circuit similar to leakage circuit 108. Each devicemay include a current sensor corresponding to sensor A1, and eachcurrent sensor may sense a different current, with the magnitude eachsensed current indicating a proximity to the system power bus. Forexample, using the numerical example indicated in FIG. 17A, when each PVdevice 107 a, 107 b . . . 107 k includes a leakage circuit coupled tothe “low voltage” output of a power converter 211, and each PV deviceincludes an identical resistor R=100 kΩ, PV device 107 a may sense acurrent of approximately

$\frac{0V}{100k\Omega} = {0{A.}}$

PV device 107 b may sense a current of approximately

$\frac{25V}{100k\Omega} = {0.25{{mA}.}}$

PV device 107 c may sense a current of approximately

$\frac{55V}{100k\Omega} = {0.55{{mA}.}}$

PV device 107 j may sense a current of approximately

$\frac{650V}{100k\Omega} = {6.5{{mA}.}}$

PV device 107 k may sense a current of approximately

$\frac{660.7V}{100k\Omega} = {6.607{{mA}.}}$

It may be observed that the closer a PV device is to the power bus, thehigher the magnitude of the sensed current may be, and in someembodiments, it may be possible to estimate the relative order of the PVdevices 107 a . . . 107 k with regard to the power bus by comparing thecurrent magnitude sensed by each PV device.

Reference is now made to FIG. 17 b , which shows a leakage circuitaccording to an illustrative embodiment. PV device 1007 may be usedinstead of PV devices 107 in FIG. 17A. For example, PV devices 107 a-107k of FIG. 17A may be replaced by a corresponding plurality of PV devices1007 a-k. PV device 1007 may comprise controller 214, power converter211 and communication device 212, which may be the same as controller214, power converter 211 and communication device 212 of FIG. 17A. PVdevice 1007 may feature a leakage terminal (LT) similar to that of PVdevice 107. Leakage circuit 1008 may comprise voltage sensor V1 andresistors R1 and R2. Resistor R2 may have a very large resistance, suchas 100 MΩ, 1GΩ, 2GΩ or even 10GΩ. R1 may be substantially smaller thanR2. For example, R1 may have a resistance of under %1 of R2. Ahigh-impedance current path may be provided between leakage terminal LTand the ground, via resistors R1 and R2. R1 and R2 may be of sufficientresistance to hold leakage current to a small value, which may reducelosses due to the leakage current. For example, R2 may be 5GΩ and R1 maybe 10 MΩ, for a total resistance of 5.01GΩ. When the voltage at LT is500V, the leakage current may be about 100 μA. Voltage sensor V1 maymeasure the voltage across resistor R1. Since R2 may be much larger thanR1. R2 may absorb the majority of the voltage drop at leakage terminalLT. As an illustrative example, assume that R2 is 99 times as large asR1, resulting in R2 absorbing 99 percent of the voltage drop at LT, andR1 absorbing 1 percent of the voltage drop at LT. When a series of PVdevices 1007 are serially coupled, each having a leakage terminal and aleakage circuit 1008, each respective voltage sensor V1 of eachrespective leakage circuit 1008 may measure a voltage equal to about %1of the voltage at the respective leakage terminal. By determining arelative order in magnitude of the respective voltage measurements, anorder of the serially-coupled PV devices 1007 may be determined (such asby a centralized controller which may receive the voltage measurementsmeasured by the respective voltage sensors).

FIG. 18 is a flow diagram of a method for determining the order of powerdevices within a PV string, which may be similar to the PV stringillustrated in FIG. 17A. At step 170, some power devices may beconsidered “unsampled,” such as power devices at which leakage currentshave not been sampled. At step 171, a power device from a group ofunsampled devices may be selected. In some embodiments, a device may beselected from a group of unsampled devices at random. In someembodiments, a device may be selected from a group of unsampled devicesaccording to predetermined criteria, such as according to an estimatedlocation within a PV string. At step 172, a power device selected atstep 171 is commanded to activate the power device's leakage circuit. Apower device command may be received via various communication methods,for example PLC and/or wireless communications, and the command may besent by a system management unit. At step 173, upon reception of acommand to activate a leakage circuit, a power device's leakage circuitmay be activated. A leakage circuit may be similar to the oneillustrated in FIG. 17A, and an activation of a leakage circuit maycomprise setting the switch Q to the ON position. A current sensorsimilar to the sensor A1 illustrated in FIG. 17A may measure a leakagecurrent obtained when Q is at the ON position. At step 174, a leakagecurrent may be measured and the measurement may be saved to a datalogging device. The data logging device may comprise flash memory,EEPROM or other memory devices. At step 175, the power device selectedat step 171 may be removed from the pool of un-sampled devices, and acommand may be issued to the power device to deactivate the powerdevice's leakage circuit. Deactivation may comprise setting the switch Qto the OFF state. At step 176 the method may determine when additionalpower devices are to be sampled. In some embodiments, method may samplethe leakage current of each power device in the string, and as long asthere is at least one power device which has not yet activated itsleakage circuit, the method may loop back to step 170. In someembodiments, the method may proceed to step 177 even when some powerdevices have not yet activated their respective leakage circuits. Atstep 177, the logged leakage current measurements may be compared, andbased on the measurements, a relative order of power devicescorresponding to the leakage current measurements may be estimated. Forexample, when three leakage currents have been measured, for exampleI_(A), I_(B), I_(C), with the three current measurements correspondingto power devices D_(A), D_(B), D_(C), and when I_(A)<I_(B)<I_(C), thenthe method may determine that D_(C) may be the closest device of thethree to the power bus, and that D_(A) may be the farthest of the threedevices from the power bus. When leakage currents of all power devicesin a PV string have been sampled, it may be possible in some embodimentsto determine the order of all of the power devices in the string.

Reference is now made to FIG. 19 , which illustrates a portion of aphotovoltaic installation and a mapping Unmanned Aerial Vehicle (UAV)according to an illustrative embodiment. Photovoltaic (PV) installation199 may comprise PV modules 191. One or more Unmanned Aerial Vehicles(UAV) 190 may be used to obtain Estimated Layout Map (ELM) of PVinstallation 199, such as to determine the relative order and/orlocation of PV modules 191. PV modules 191 may comprise PV generators(such as one or more PV cells, PV strings, PV substrings, PV panels. PVshingles, and/or the like) coupled to photovoltaic power devices (suchas PV optimizers, DC/DC converters, DC/AC inverters). In someembodiments, each PV module 191 may comprise an identification label (IDlabel) which may be readable by UAV 190. The ID label may be a barcode,serial number, RFID tag, memory device or any other medium forcontaining information that may be read by an external device, with UAV190 comprising an appropriate device for reading the ID label. Forexample, each PV module 191 may have an RFID tag, while UAV 190 may havean RFID reader. In some embodiments, each PV module 191 may have abarcode sticker, tag, while UAV 190 may have a barcode scanner. UAV 190may have various functional devices similar to those comprising combineddevice 700 of FIG. 7 . For example, UAV 190 may comprise controller 195,communication device 196, GPS device 194. ID reader 193, and datalogging device 192, which may be similar to or the same as ID reader203, GPS device 201, data logging device 202, controller 205, andcommunication device 206 of FIG. 7 .

In some embodiments, UAV 190 may automatically read the ID tag of eachof PV modules 191. In some embodiments. UAV 190 may be in proximity toeach PV module at the time the PV module's ID tag is read, and use GPSdevice 194 to estimate the coordinates of the PV module being scanned.The method of FIG. 2A may be used to generate an ELM of the PVinstallation using the measured or estimated GPS coordinates of the PVmodules.

UAV 190 may be variously realized. For example, a drone, miniaturehelicopter, remote-controlled airplane or various other UAVs may beutilized.

In some embodiments, UAV 190 may comprise a thermal camera. For example,camera 197 may be a thermal camera for obtaining a thermal image of PVinstallation 199, and by taking multiple thermal images of PVinstallation 199 over time, relative locations of PV modules may beestimated for generating an ELM, using methods disclosed herein.

Reference is now made to FIG. 20 , which illustrates thermal propertiesof photovoltaic generators (such as photovoltaic panels) which may befeatured in accordance with methods and apparatuses disclosed herein.Some types of photovoltaic panels may generate increased heat whenphotovoltaic power generated by the panel is not provided to anelectrical load. Photovoltaic power may be generated by a PV panel as aresult of photovoltaic cells mounted on the PV panel absorbing solarirradiance. When an electrical load is coupled to a PV panel, some ofthe absorbed solar irradiance may be converted to electrical powerprovided to the load. When no electrical load (or a reduced electricalload) is coupled to the PV panel, an increased portion of the absorbedirradiance may be converted to heat, which may result in an increasedtemperature of the PV panel. When an electrical load is coupled to a PVpanel, but the load only draws a small portion of the PV power producedby the panel, the panel temperature may be lower than the temperaturewhen compared to the “no-load” case, but may be higher than thetemperature that would be measured when an electrical load drew anincreased amount of PV power from the PV panel.

With reference again to FIG. 20 , this figure shows an illustrativethermal image of a group of PV generators (which may be used as PVmodules 191 of FIG. 19 ). PV generators 2001 b may be providing a firstlevel of electrical power (such as 300 watts) to a load, PV generators2001 c may be providing a second level of electrical power (such as 200watts) to an electrical load, and PV generators 2001 may be providing athird, lower level of electrical power (such as 50 W) to an electricalload, or might not be providing any electrical power to a load. All ofPV generators 2001 a-2001 c may be irradiated by substantially the samelevel of solar irradiance. As indicated by temperature bar 2002, areduced provision of electrical power to a load may increase atemperature of an associated PV generator in a manner (such as by about4° C.) which may be visually detectable by a thermal image.

With reference yet again to FIG. 20 , which illustrates a thermal imageportion of a photovoltaic string according to an illustrativeembodiment. PV panels 2001 a-2001 f may be coupled in series or inparallel to form part of a PV string. At the time the thermal image wasobtained. PV panels 2001 a-2001 e were coupled to an electrical load,and PV panel 2001 f was not coupled to an electrical load. PV panel 2001f may be observed to be visually distinguishable compared to PV panels2001 a-2001 e.

Referring back to FIG. 19 , camera 197 may be used to obtain thermalimages similar to the thermal images illustrated in FIG. 20 , withcontroller 195 configured to implement a method for determining an ELMfrom images obtained by camera 197. A succession of thermal imagessimilar to the images of FIG. 20 may be obtained and stored in datalogging device 192, with controller 195 configured to read the imagesfrom data logging device 192 for processing.

Reference is now made to FIG. 21 , which illustrates a method forinstallation mapping according to one or more illustrative aspects ofthe disclosure. Method 2100 may be carried out by a controller comprisedby a UAV (such as controller 195 of FIG. 19 ), or by a system-levelcontroller in communication with PV modules and/or a UAV, or by acombination thereof. For illustrative purposes, it may be assumed thatmethod 2100 is carried out by controller 195 of FIG. 19 and applied toPV modules 191 of FIG. 19 . Each PV module 191 may comprise a PV powerdevice capable of increasing or decreasing the electrical power drawnfrom the PV model. For example, in some embodiments, each PV module 191may comprise a disconnect switch configured to disconnect the PV modulefrom a string of PV modules which coupled to an electrical load. Bydisconnecting a selected PV module from the string of PV modules, theselected PV module may cease providing power to the electrical load, andthe temperature of the selected PV module may rise. In some embodiments,each PV module 191 may be coupled to an optimizer, each optimizerconfigured to increase or reduce the power drawn from the correspondingPV module.

PV power devices coupled to PV modules 191 may be in communication witha controller carrying out method 2100 or part thereof. For example, PVpower devices coupled to PV modules 191 may comprise wirelesscommunication devices configured to communicate with communicationdevice 196 of UAV 190.

Method 2100 may be applied to a group of PV modules without regard forinterconnectivity. Method 2100 may effectively map PV modules which areelectrically connected (such as modules which are part of the same PVstring) and may effectively map PV modules which are not electricallyconnected (such as modules which are part of different PV strings).

At the start of method 2100, at step 1220, all PV modules in the groupare considered “untested”. At step 1221, a controller (such as thecontroller carrying out method 2100 or part of method 2100) may select aPV module from the pool of untested PV modules. At step 1222, thecontroller reduces the electrical power drawn from the selected PVmodule. For example, the controller may command a PV power device (suchas a disconnect switch or an optimizer) coupled to the PV module toreduce the electrical power drawn from the PV module (such as bydisconnected the PV module from a load, or by operating the PV module atan operating point which reduces the power drawn from the PV module.

After the electrical power drawn from the PV module is reduced, it maytake several minutes for the temperature of the PV module tosubstantially rise. The controller may wait for a period of time (suchas 3, 5, 10 or 20 minutes) before proceeding to step 1223.

At step 1223, the controller may control a thermal imaging device (suchas camera 197) to obtain a thermal image of the group of PV modules. Atstep 1224, the controller may analyze the thermal image to find “hotspots”, e.g., areas in the image which indicate a higher temperature. Insome embodiments, the thermal image may comprise temperaturemeasurements which may be numerically compared. In some embodiments, thethermal image may be represented by pixels of varying colors and/orshades of gray, with the controller configured to process the image anddetect areas comprising pixels which may be indicative of a highertemperature (e.g. red, or darker shades of gray).

At step 1225, the controller may estimate the relative location of a hotspot detected at step 1224. For example, the controller may determinethat the group of PV modules comprises nine PV modules placedside-by-side (e.g. similar to the depiction of FIG. 20 ), with thefourth PV module from the right (i.e. PV module 2001) hotter than therest. In some embodiments, the controller may have estimated physicalcoordinates of one of the PV modules, and may use the estimatedcoordinates as an “anchor” node for estimating locations of the other PVmodules. In some embodiments, the controller may determine a relativeordering or relational placements (e.g. to the right of, to the left of,in front of, behind) of the PV modules in the group, and aggregate therelational placements to generate an ELM.

In an embodiment, method 2100 may be adapted to have all PV devicesinitially not providing substantial power to an electrical load. Themethod may be adapted at step 1222 to increase the electrical powerdrawn from the selected PV module, at steps 1224-1225 to detect andestimate “cold spot” locations, and at step 1226 to decrease theelectrical power drawn from the selected PV module.

At step 1226, the PV module selected at step 1221 is removed from thegroup of untested PV modules, and the power drawn from the selected PVmodule is increased (e.g. by commanding a disconnect switch to reconnectthe PV module to an electrical load, or commanding an optimizer tooperate the PV module at an increased-power operating point).

At step 1227, the controller determines if untested PV modules remain,i.e., if there are PV modules in the group which have not yet beenselected at step 1221. If untested PV modules remain, the controller mayloop back to step 1221. If no untested PV modules remain, the controllermay proceed to step 1228.

At step 1228, the controller may aggregate the hot spot locationsestimated at step 1225 over the method iterations, to produce anestimated ELM.

In an alternative embodiment, thermal images obtained at step 1223 maybe saved to memory, with steps 1224-1225 carried out after the finaliteration of step 1227. In other words, analysis of thermal images maybe delayed until after a full set of thermal images (one per iterationthrough steps 1221-1227) has been obtained. In a preferred embodiment,steps 1224-1225 are carried out in the order indicated in FIG. 21 , toenable the controller to repeat iterations if needed. For example,method 2100 may comprise an additional step of ensuring that a “hotspot” has been detected at step 1224, and in the event that the methodhas not identified a hot spot in the thermal image obtained at step1223, having the method loop back to step 1221, or alternatively, waitan additional several minutes and then loop back to step 1223.

Method 2100 may be combined with other methods disclosed herein, forexample, to increase the accuracy of ELMs and PIMs generated by methodsdisclosed herein. For example, method 2100 may be used to obtain aninitial ELM, with the method of FIG. 18 used for validation (orvice-versa).

In some embodiments, reference was made to “upper” and “lower” junctionbox portions. This language was used for ease and is not intended to belimiting. In some embodiments, the two portions may be side-by-side,and/or functional circuitry may be transferred from one junction boxportion to other, in a manner that allows them to be in electricalcommunication when coupled to one another.

In the illustrative embodiments disclosed herein, PV modules are used toexemplify energy sources which may make use of the novel featuresdisclosed. In some embodiments, the energy sources may includebatteries, wind or hydroelectric turbines, fuel cells or other energysources in addition to or instead of PV modules. The current routingmethods and other techniques disclosed herein may be applied toalternative energy sources such as those listed above, and thementioning of PV modules as energy sources is for illustrative purposesonly and not intended to be limiting in this respect. For example, anyother energy sources or combination of energy sources may be used.

It is noted that various connections are set forth between elementsherein. These connections are described in general and, unless specifiedotherwise, may be direct or indirect; this specification is not intendedto be limiting in this respect. Further, elements of one embodiment maybe combined with elements from other embodiments in appropriatecombinations or subcombinations.

Specific dimensions, specific materials, specific ranges, specificfrequencies, specific voltages, specific impedances, and/or otherspecific properties and values disclosed herein are example in natureand do not limit the scope of the present disclosure. The disclosureherein of particular values and particular ranges of values for givenparameters are not exclusive of other values and ranges of values thatmay be useful in one or more of the examples disclosed herein. Moreover,it is envisioned that any two particular values for a specific parameterstated herein may define the endpoints of a range of values that may besuitable for the given parameter (for example, the disclosure of a firstvalue and a second value for a given parameter may be interpreted asdisclosing that any value between the first and second values may alsobe employed for the given parameter). For example, parameter X isexemplified herein to have value A and also exemplified to have value Z,it is envisioned that parameter X may have a range of values from aboutA to about Z. Similarly, it is envisioned that disclosure of two or moreranges of values for a parameter (whether such ranges are nested,overlapping or distinct) subsume all possible combination of ranges forthe value that might be claimed using endpoints of the disclosed ranges.For example, when parameter X is exemplified herein to have values inthe range of 1-10, or 2-9, or 3-8, it is also envisioned that parameterX may have other ranges of values including 1-9, 1-8, 1-3, 1-2, 2-10,2-8, 2-3, 3-10, and 3-9.

Experimental Results

Parasitic leakage from the DC+ and/or DC− lines of a power device toground may be dominated by the leakage from the power device over othersources. For example, the device leakage may be approximately 250 pf(e.g., from MOSFET spreaders to the power device chassis) and solarpanel leakage to enclosure may be approximately 100 pf. The PV stringpower devices' impedance, such as from switch bodies, inductors,capacitors, and/or leakage capacitances, may be modified using switchesconfigured to tune the impedance to a mapping signal frequency, such asusing switches that connect capacitors and inductors in series orparallel. For example, the switches may adjust the impedanceincrementally until a best match is found to the tuning signal. Thesignal frequency may be tuned or adjusted to the devices' impedances,such as an adjustable frequency transmitter searching for an optimalfrequency based on a fixed set of impedance changing components beingconnected. A spread spectrum signal injection may be used to send aplurality of signal frequencies to the power devices. Each power devicemay collect and record the attenuation during the frequency changes,send the recorded signal back to the central processor, and the centralprocessor may analyze the signal strength at each frequency to determinethe correct order of power devices along the string. Correspondingsignal receivers at each power device may be tuned to a fixed signalfrequency or be broadband receivers for receiving signals at multiplefrequencies.

A high frequency (HF) signal (e.g., 140 kHz) may be injected to one sideof the PV string conductor, and an amplitude reduction during the signalpropagation along the PV string may be observed. A processor maydetermine the power devices' order within the PV string based on theinjected signal being gradually attenuated by each device along thestring. The device leakage may be between 50 and 500 pf, and the solarpanel leakage may be between 20 and 350 pf. Depending on the leakagevalues of a specific installation, the HF signal frequency may bebetween 20 kHz and 500 kHz, where a higher frequency of this rangeallows more attenuation between adjacent devices, but also may causedevices further down the string to reach saturation and for the signalstrength to become flat. Furthermore, as the signal may enter the PVstring from both the DC+ and DC− sides of the string, and the signal andleakages are relative to ground, the signal injected at DC+ may alsoreach the DC− side of the string. This may result in a monotonicallydecreasing signal strengths at each device up to a certain point in thestring, and then the signal strengths may increase due to the signalarriving at the device from the DC− side. The signal may be configuredsuch that the leakage impedances may optimally attenuate the signalstrength along the entire string.

FIG. 22 shows an example circuit diagram of a PV string with PV orderdetection components. A central processor or central power device (notshown) may include capacitor(s) at cx and a common mode choke at CM.Terminals DC+ and DC− may be connected to a string of power devicesDev1, Dev2, . . . , DevX, each power device being connected to a PVpanel (not shown). Connections to ground cy1 and cy2 allow the injectedsignal to propagate through the string and attenuate to ground throughthe leakage capacitors Leak1, Ieak2, . . . , LeakX. Serial inductor L1may be used to assist in measuring the signal attenuation at each deviceas it may prevent the signal from entering the reverse side of the PVstring. A transmitter as at Trans may inject a signal at a highfrequency, such as 140 kHz, into the DC+ side of the PV string or theDC− side of the PV string (not shown). The cables of the PV string mayhave impedance or inductance of Lcable. Each power device along thestring, as at Dev1, may include serial output capacitor Cout in serieswith parallel inductor Lcomm and capacitor Cr. Leakage capacitors Leak1,Leak2, . . . LeakX may attenuate some of the signal strength by leakingsome of the signal to ground.

Prior to injecting a signal at one end of the PV string, the other endof the string may be grounded to form a closed loop to ground. To obtainbetter signal attenuation along the PV string, a large impedance may beserially connected between the DC+ or DC−, on the opposite side from thePV string, and past the signal injection points and ground connectionpoint. For example, a 150 kHz signal may be injected (with respect toground) on the DC+ end of the PV string conductor. The signal may beinjected from the DC+ end of the string and the DC− end of the stringmay be shorted to ground, or vice versa. Signal strengths at each PVpanel along the string are measured, for example signal strength at thepower devices along the string, such as junction boxes, powerconverters, optimizers, micro-inverters, or the like, associated witheach PV panel. A serial inductance may be added in series to the DC−conductor, after the ground connection, such as an inductor of 0.1 mH to10 mH. The serial impedance may help limit the amount of signal thatreaches the opposite end of the string, limiting the “bathtub curve” andimproving the accuracy of the mapping. Using a higher signal frequencymay provide better attenuation from the power devices, but may alsoreach saturation quicker. To overcome the saturation, the side of the PVstring used for signal injection may be reversed, for example the signalis injected from the DC− end, a 1 mH inductor is serially coupled to theDC+ end of the string, and the DC+ end is shorted to ground. The reverseinjection may be especially suitable for long strings.

FIG. 23 shows example graphs of signal attenuations from signalinjection on DC+ and DC−. Graph 2300 shows the decrease in signalstrength along the PV string when the signal is injected from the DC+terminal, where the increase from power device 15 to 20 is due toleakage of the signal from the DC− terminal. Graph 2310 shows thedecrease in signal strength along the PV string when the signal isinjected from the DC− terminal, where the increase from power device 5to 1 is due to leakage of the signal from the DC+ terminal.

The serial inductance may saturate at power generation currents throughthe string, for example, a serial inductance of 1 mH may saturate atcurrents through the PV string higher than 0.2 A, such as during normaloperation (e.g. after the mapping is completed). The power devicereceiver may switch to the tuned frequency of 140 kHz during the mappingand when the mapping is complete return to a normal communicationfrequency, such as 60 kHz or the like. Each of the power devices mayreceive a reduced signal strength in proportion to the power device'sposition along the string from the injected signal. After mapping, suchas after a predefined time limit, each power device may transmit thereceived signal strength value back to a central processor or powerdevice.

The central processor may determine the order based on the receivedsignal strength measurements at each solar panel. The mapping may beverified or confirmed by repeating the mapping at a slightly differentfrequency, impedance values at each device, or both. By comparing themapping order between two or more different mapping measurements, it maybe determined that the mapping is accurate, or that there may bedifferent leakage from some of the devices. A spread spectrum signal mayallow collecting multiple signal frequencies at once and comparing theorder determined at each frequency may help confirm the solar panelorder. For example, sending a signal at a fixed frequency, and adjustingimpedances during different mapping tests to different impedance valuesfor each test may confirm that the results of the solar panel order arecorrect. When the order at different frequencies or different deviceimpedance levels is different, the power device or solar leakages may bedifferent, and adjusting the power devices to different impedance valuesmay help determine and confirm the correct order of panels along thestring.

1. A method comprising: receiving, by at least one power device of aplurality of power devices, a signal from each power device of theplurality of power devices; determining, based on strengths of thereceived signals, an order of the plurality of power devices; andstoring the order of the plurality of power devices.
 2. The method ofclaim 1, wherein the signal from each power device of the plurality ofpower devices comprises an identification of a respective power deviceof the plurality of power devices.
 3. The method of claim 1, wherein thesignal from each power device of the plurality of power devicescomprises power line communication signals.
 4. The method of claim 1,wherein the determining the order of the plurality of power devices isfurther based on a map, wherein the map comprises locations of theplurality of power devices and does not specify identities of theplurality of power devices.
 5. The method of claim 1, wherein theplurality of power devices are connected in a serial string.
 6. Themethod of claim 1, wherein the determining the order of the plurality ofpower devices is further based on a known location of at least one ofthe plurality of power devices.
 7. The method of claim 1, wherein thereceiving the signal from each power device of the plurality of powerdevices is performed multiple times for each of the at least one powerdevice, and wherein the determining the order of the plurality of powerdevices comprises averaging the strengths of the received signals. 8.The method of claim 1, wherein the determining the order of theplurality of power devices is further based on analyzing pairwisedistance estimates among the plurality of power devices.
 9. The methodof claim 8, wherein the determining the order of the plurality of powerdevices is further based on minimizing a disparity among the pairwisedistance estimates.
 10. The method of claim 1, wherein the determiningthe order of the plurality of power devices is further based on at leastone of: simulated annealing, convex optimization, semidefiniteprogramming, or multidimensional scaling.
 11. The method of claim 1,wherein the determining the order of the plurality of power devices isfurther based on a least squares analysis of the strengths of thereceived signals.
 12. A system comprising: a plurality of power devices,wherein each of the plurality of power devices comprises a processor anda communication circuit; a central power device comprising a centralprocessor and a central communication circuit; and a plurality ofconductors connecting the plurality of power devices in a serial stringand to the central power device, wherein each of the plurality of powerdevices is configured to: transmit, using the communication circuit, afirst signal to other power devices of the plurality of power devices;receive at least one second signal from the other power devices; recorda signal strength of the at least one second signal; and send the signalstrength to the central processor, and wherein the central power deviceis configured to: determine an order of the plurality of power devicesbased on the signal strength.
 13. The system of claim 12, wherein thecentral power device is further configured to perform at least one of:storing the order of the plurality of power devices, or displaying theorder of the plurality of power devices.
 14. The system of claim 12,wherein the at least one second signal comprises an identification of arespective transmitting power device.
 15. The system of claim 12,wherein the at least one second signal comprises a power linecommunication signal.
 16. The system of claim 12, wherein the centralpower device is configured to determine the order of the plurality ofpower devices further based on a map, wherein the map compriseslocations of the plurality of power devices and does not specifyidentities of the plurality of power devices.
 17. The system of claim12, wherein the central power device is configured to determine theorder of the plurality of power devices further based on a knownlocation of at least one of the plurality of power devices.
 18. Thesystem of claim 12, wherein the central power device is configured toreceiving the at least one second signal multiple times for each of theother power devices, and wherein the central power device is configuredto determine the order of the plurality of power devices by averagingthe signal strength.
 19. The system of claim 12, wherein the centralpower device is configured to determine the order of the plurality ofpower devices by analyzing pairwise distance estimates among theplurality of power devices.
 20. The system of claim 19, wherein thecentral power device is configured to determine the order of theplurality of power devices by minimizing a disparity among the pairwisedistance estimates.
 21. The system of claim 12, wherein the centralpower device is configured to determine the order of the plurality ofpower devices further based on at least one of: a simulated annealing, aconvex optimization, a semidefinite programming, or a multidimensionalscaling.
 22. The system of claim 12, wherein the central power device isconfigured to determine the order of the plurality of power devicesfurther based on a least squares analysis of the signal strength.